Ok, my 2 cents... <- as a 7/9 in APA and 13~14 in ACS/BCA
IF you can't handle losing, then play APA. As a top player, the odds of losing a race to whatever is significantly lower than a single rack in ACS. With ACS/BCA you simply need to be ok with having an otherwise flawless evening of play producing a personal score of 34 out of a potential 85. Just the way the league works.
If you can't handle drama unassociated to actual game play, then play ACS/BCA. It's crazy but simply removing the orchestration of match ups that always seems to be the main focus in APA, makes an ACS/BCA evening run so much smoother. Everyone knows they will be playing everyone else in the opponent's roster, so that one element makes the night that much more enjoyable.
Regarding wait times... APA is the longer night. IF you happen to be a player that's catered to. You may be able to manipulate your captain into playing you first no matter what, and then if you have zero interest in supporting your teammates you can bugger off. Otherwise expect a 5hr campaign. ACS/BCA runs faster. Less opportunities for time outs, etc... Sure depending where you land in the order and if you're the visiting team, you may have a single loong wait, but that's it. My ACS night is never longer than 3hrs.
Which is tougher...? Well that depends on how good you are. I find APA infinitely easier, but again I'm at the top of the local food chain so the odds of me dropping a race are slim. ACS/BCA has that single rack element. So a single error can cost you that rack. Assuming if you even get a chance at the table. I will say that I believe the focus of players is higher within the ACS/BCA format because of the "do or die" nature of the single rack. Those losing believe it's "harder" because of the lack of opportunity.
Why I play ACS/BCA rather than APA. Well I can't be bothered with drama. I just want to compete, and I don't like having my time wasted. I also have this superpower that allows me to stomach losing single racks without it bothering me. In ACS/BCA I get to exchange pleasantries with literally everyone that plays in the league. In APA I only meet those who the captains deem I should be playing. Locally, my ACS LO maxes out his leagues and there's a wait list to get in. The local APA LO will accept anyone that has a team and will rotate the teams through nearby dives with valley BBs just to increase his revenue.
For purely competitive pool, the best format I've come across is the APA Masters. Mixed race, with rules that more closely match how the games are meant to be played. That said, in Masters, the players are like minded and those lower on the food chain know their place and don't whine about it. There is some minor orchestration of match ups, but if that matters then you're not winning anyway.