I would suggest you to try out as many jump/break as possible before you buy. A lot of cues feel wonderful when you first try them, so you need to try many different brands in order to know which is really superior. A Lot of people will tell you their jump or jump/break is awesome because they have never tried anything else or have only tried a few shots with a limited number of brands.
After all, not everyone has the extra money to buy all the brands on the market to try them all out over an extended period of time.
We did that when we invented the X Breaker and it took us about a year. But then we were doing that in order to come up with a superior product.
Also, you should test the consistency of the performance. Say, if you are trying the jump, you should try to jump many times to see how accurate and how consistent your jump is. I like to check how many miscues I get with the jump, how many times I can jump in a row without chalking, and how close I can jump with a certain cue.
Consistency is very important. You do not want to worry about a miscue when you need to jump a ball, make it, and win a game at hill-hill--you want to have 100% confidence in the performance of your cue. Also, you want to know how well a tip can hold chalk. If the tip cannot hold chalk well, then you have to resort to luck on your crucial jump in a game winning situation.
With the break, a lot of people talk about the speed, but you also need control, and a lot of breaking cues only offer control if you break with less than 100% power. You should try to break 100% and see what happen; You also should try to break with spin to see if you will miscue, because you sometimes may need to do that. Finally, when you break 100%, compare the feel and the hit to see which cue gives you the best control and power.
Hope these help.
Richard