I have played on PrimeDice and BetKing. Both of them are great actually with better user interface and fast payouts. Dice games are best in PrimeDice right now and it is one of the top Dice gaming websites.

I would say Primedice is the best to play Dice.
I think they will if the roll speed increase. Now it's kinda slow.

Based on my experience, in automated betting, it is faster now compared to the previous version. Disabling the animation makes the rolls faster.
Disabling animation can really make rolls more faster compared when its enabled depending on a dice on having such feature. When it comes to primedice no doubt this is one of the best dice site in the market today.
Choosing up a site would matter on users preference yet we do have different taste and we would definitely stick out on where we are comfortable.
Yes if it comes Dice game most of the people will prefer Primedice this is a very old casino and have more reputation in this forum, you can also try Bitlser at present this is the number one casino for slot games. Quick withdraw and deposit and customer support is also excellent very quickly they will solve your issues and they can allow you to play with multiple altcoins. Now Bustadice is also gaining popularity in the market so you can pick which is more comfortable for you.