I use only Questrade so I cannot comment on Interactive.
Questrade's interface is functional. I can view what I have, buy equities, and manage my account. At this point I am fairly Couch Potato so I use Questrade for only five minutes a month. Fifteen during tax time. If there are advanced widgets and gadgets with horrible UX and a UI that brings women to tears, I simply haven't encountered it. For my use case, it is pretty nice. They recently revamped their UI and surprisingly it made the service even easier to use.
The fees, being zero, are nice. They've recently been lowered.
When I was chooisng my discount broker, I did read outdated complaints. From my understanding, the UI was pretty poor in the past but has come a long way. Pro-tip though: disable margin trading when setting up an account because, I'm told, it can be easy to accidentally use it in a transaction. No idea if it is because I've had it turned off since the beginning. I've heard a similar complaint when making purchases in other currencies; I stick to CAD on the TSX so I haven't experienced these either.
If I did have a critique, it would be with the Profit/Lost indicator. It currently states I have a P/L of X. This is just (current price of assets) - (price of assets at purchase). It ignores that I've gotten dividends from assets I own. I am told this is a common formula. I think it is stupid. In other words, even simple old me finds the performance tracking is too simply for what I need.
