I think that probably depends on what is important to you. *note - both of our contracts were purchased through DVCRM, so I don’t have personal experience with Fidelity*
I don’t like Fidelity’s site as it doesn’t filter as nicely as DVCRM…multiple filter options make it easier to find what you’re looking for, like a small April UY contract, without wading through all of the contracts you’re not interested in. I’ve also seen too many posts on FB from people making offers through Fidelity experiencing communication issues regarding their offers (slow response, not getting updates, etc) while we’ve had fabulous communication through 3 (I think?) contracts
DVC exercised ROFR on and the 2 contracts that DVC waived ROFR on in the past year. I’m anxious enough about the contracts I want, so I appreciate the level of communication from DVCRM, so if I’m paying a little more than the lowest price listed on Disboards, it’s worth it to me!