It mostly between the IC discord and StakesUnited. I have most of mine in the Discord, a few in SU and some more in my wallet. I find that over time, they are fairly equal in terms of earnings rate. SU requires a bit of a wait to get your coins out which I am not too keen on and in my view is the highest risk being an outside body. I am still waiting on them releasing a bit of dust I have had there for over a month. Discord is much quicker to get your coins back from and I can usually have them back in my wallet in less than half an hour (Unconfirmed usually appears pretty much instantly). I also feel a bit safer with them. Wallet is really weird with some times a stake per day and other times noting for a few days and then other times I get 5 stakes in a day. Over time I think it averages out quite nicely. Wallet feels safest.