I tried a number of account aggregators for several weeks last year: Emma, Yolt, MoneyHub, Money Dashboard, and HSBC Connected Money.
Of these, I prefer and have settled on Emma. I think the main reason is I like that attention seems to be given to providing rich transaction information in Emma (actual merchant names, logos, notes field, transaction history with merchant). This is not done as well, or at all, in other aggregators. I also found syncing in Emma to incredibly reliable and fast compared to the other aggregators. At least this was the case last year when I was directly comparing. This year, occasional syncing issues seem to have crept it to Emma with some banks. Hope this is just temporary.
Now I only use Emma and Yolt. I keep Yolt around simply to provide access to Sainsbury’s bank which is not supported in Emma.
Have just taken a look at Bankin after I saw it mentioned at the top of this thread. Have not tried it out thoroughly yet, but I have noticed it has one feature which I wish Emma had. I have a thread about that here.