The big difference is momentum. You don't really get to build any playing alternate break. Plus there's also the argument of not being able to make big comebacks playing alt. break (see Shane coming back from 10-3 v Mika at WPC).
I think an alternative that allows both of those things would be to play winner breaks until someone gets to the hill. Once a player gets to the hill, the trailing player gets all of the breaks. If it gets to hill-hill, relag for the final break.
I think the effects of momentum are exaggerated. Even if true, only one guy has it, while it is doing the exact opposite for the other guy, getting him cold and out of stroke so that when he comes to the table he is not at his best so if it is doing the exact opposite for one of them is there really a net benefit? Doesn't seem like there is. In any case alternate break puts more pressure on the players as they feel even more like they have to make the most of every trip to the table. Increased pressure, and ensuring that both players are more in stroke and are forced to give every last ounce of everything they have on every shot, both seem like good things to me.
As for the comebacks under alternate break, it has been covered before but a few points.
First, big comebacks aren't very common in winner breaks either and in fact are pretty rare in the scheme of things. They are so few that we talk about them when they occur and remember them (remember that big one Kim Davenport made in the early 90's?), a recent example being SVB's comeback against Mika. It's not like they are happening every other match or even every other tournament.
Second, that big comebacks aren't possible in alternate breaks is ludicrous. Anybody that says that can't watch much pool because we get to see it happen often enough with our own eyes, but logic alone tells you it can happen. The opponent managed to get way ahead didn't he? The same way the one guy was able to get big ahead is the same way the other guy can make a big comeback too.
Third, the big come backs happen in alternate breaks what seems like just about as often, although there are obviously fewer overall simply because there are fewer alternate break events overall, but they seem to happen often enough under that format too so I don't know that the rate at which they happen under winner breaks is really all that much more. It sounds intuitive that they would but the anecdotal evidence doesn't seem to indicate a massive difference. It would be interesting if someone tracked it over a long period of time to see just how much difference there is.
Fourth, to whatever extent there are less big comebacks in alternate breaks, you don't need them because alternate breaks keeps the matches much tighter and doesn't allow anybody to get a massive lead to begin with all that often. That results in a significantly greater percentage of the matches being close and exciting whereas in winner breaks a significant portion are lopsided and unexciting and where you end up losing all the excitement and much interest as soon as somebody gets a big lead. On a yearly basis is it really worth having thousands more lopsided matches that get boring as hell as soon as somebody gets a good lead just so you can have that one more match a year with a big comeback? Thousands more boring matches for one more exciting one just doesn't sound like a good trade off at all to me, especially when you can have thousands more exciting matches and only give up one exciting one.
To recap, big comebacks are rare to begin with in winner breaks, they still happen plenty often in alternate breaks, and they aren't needed much in alternate breaks to begin with because alternate breaks keeps most of the matches close and exciting unlike winner breaks where a big percentage, perhaps the majority, get to be lopsided snooze fests. What you give up to get that rare additional big comeback if that is even the case just doesn't seem to even be close to all that you are giving up in return.
I'm personally convinced that the big opposition to alternate breaks is that it just isn't what we are used to, and if it is all we had for a while to where we really got used to it being the way it is now most wouldn't want to go back. Every other major sport on earth has something along the lines of alternate breaks that ensures both sides get similar offensive possessions. I never hear anybody complaining about how the scoring team in football should be receiving the next kickoff and shouldn't have to turn over the ball to the other team until they have failed to score, and screw the other team if they never get an offensive possession, that would be "exciting". I never hear anybody complaining about how the scoring basketball team should keep possession of the ball every time they make a basket, and screw the other team if they never get an offensive possession or have to go a long period of time without an offensive possession, that would be "exciting". All the same arguments used for winner breaks in pool apply exactly the same to every other sport on earth and yet nobody is making them for any other sport, and the only reason we want the scoring side to retain offensive possession in pool is simply because it is the way it has always been and what we have been used to our whole live but as with every other sport alternate makes more sense and overall makes for a better and even more exciting game on net.
As far as your idea of winner breaks until it gets to the hill, and then the trailing player gets all breaks from there (except the where you lag for the last break if it goes hill hill), I hate the idea of any form of loser breaks. I am firmly against giving somebody some help just because they are behind. Why don't we just give the player that is behind the wild 8 spot (in 9 ball) until they get caught back up instead or also? Same thing as loser breaks in my mind, I just can't justify the fairness of it as they haven't earned it, and in fact not only was it not earned, but it is a handout that is rewarding failure. With alternate breaks, where both players get equal offensive chances, it can't be argued that it isn't fair as that is as fair as it possibly gets, and obviously both sides are entitled to participate because the whole point is to see who is the better player that day which can't be done unless both player's get equal offensive chances. With winner breaks you at least have the lame argument that they did something to earn the next break (they scored), although it still isn't the best format for determining the better player since somebody can be kept from even being able to participate and finding the better player at that moment is supposed to be the whole point of the match so winner breaks doesn't make the best sense either.
If you want to see who can put together the biggest packages then just do a "playing the ghost" tournament. If you want to see who is actually the better player that day between two players then do alternate break where there can be no argument against the fact that alternate breaks best does that. Under no circumstance though can I think of a good reason to use loser breaks to give unearned handouts and to reward failure. Since we are trying to find the best player alternate breaks is the format that makes the most sense, and it just so happens to come with a lot of other benefits too and has essentially no drawbacks other than it isn't what we are used to yet.
