I've not done a driver experience on the Epping and Ongar, I have done a few diesel cab rides at their diesel galas. I have done several 'driver experience' sessions elsewhere (mostly steam, but one class 20 diesel) as part of a group sharing the 'driving experience' to keep the cost per person down. The EOR cab rides have included class 33, 37, 03 and I think another that I can't remember.
With the sawtooth gradient profile of the EOR I think it's a great place to be in the cab - especially the standing start on the steep gradient in Epping Forest at that end of the line. I particularly remember doing that as a cab ride on the cl. 33, when after he'd got the train moving the driver asked the person looking after the (visiting) loco if it was OK to 'open it up'... if you're a 'diesel head', it doesn't get much better than blasting up a steep gradient in a cutting with a Sulzer 8LDA28 on full power
That said, and despite being a diesel head myself, I think driving steam (especially the smaller/older locos) is more fun/interesting than driving a diesel. My favourite was a drive of the
ex-GER Y14 (an 0-6-0 tender loco) at the North Norfolk Railway up the hill out of Weybourne towards Holt - once I'd got it properly moving (and stopped it slipping) it was 'reduce the cut-off' and 'open it up' time for the climb... it might have been 100+ years old but it certainly wasn't lacking in performance (or noise!).
Every time I've done a 'driver experience' with a group of people in the past everyone has enjoyed it, so I'm sure you would too.