Party's vip system is worse than Stars. I played there when I first moved out of the U.S and it was the biggest waste of 2 months ever
. I think I got like $150 grinding 100k hands at 25nl-50nl or something retarded.
Merge's traffic is solid for 25nl and under. Sometimes during 4am-7am Est (new york time) their are few 50nl games going, but other than that I haven't seen many problems. Only once or twice have I found 6 tables or less on 25nl and that was during that 4-7 window.
Personally I love Stars. However, I'm the same as you and want ********. Stars has great software and tons of games. But tbh I kind of like Lock Poker's (merge skin) look/software, it only took me a day or two to get used to it.
There's also Microgaming which I think has 30% flat ******** thru Leggo. I played there briefly, software seemed decent, I think the traffic during non peak hours isn't great. Ongame i hear is super soft, but again the traffic isn't great. However if you're playing 4nl-25nl I think any site will have a decent amount of games going at any time.