I just considered another major advantage of UB. On Party losers muck their cards even if they see the bets on the river (unlike the rules in any B&M casino). If you look at the hand histories you do not see what they held.
UB does give you their cards if they see the bets on the river.
This is important if you are trying to understand your opponents. What kinds of hands do they play? How much are they bluffing; how much did you just have a slightly better hand?
I use the hand histories on UB because they are much more informative. IMHO this is a major weakness of Party!
Remember, if you want to join UB email me and get the "friend" referral bonus (disclosure - I win also). I will give you my UB name to receive the bonus.