Vanguard lacks some features, and isn't super user friendly. Having used Schwab extensively in the past, I would say Schwab is better. I've briefly used Fidelity, but mostly through the NetBenefits portal for my 401(k), which isn't quite the same thing. Based on limited sample size, I'd say Vanguard slots in just above Fidelity for usability.
What specifically about depositing funds is a PITA? I haven't had that specific frustration. Click buy, say what you want, fund from XYZ bank account, donezo.
The one missing feature that really bumps me (and was available on the old-school accounts before everyone was switched to brokerage) is the ability to direct dividends from one fund into another fund. So simple, you'd think they would have added it by now...