I have a 3 wheeler and a 4 wheeler. I prefer the 4 wheeler by a long way, but they're very different prams so it's really comparing apples with oranges. However, I agree with the PP who said that the 4 wheeler is much easier when using public transport.
You can Lock-off a 3 wheelers front wheel before getting on a train - easy to do
then it will be more stable.
You can do that, but then it makes it hard to maneuver around the platform to get to the train, or around the ignorant passengers on the train so that you can get off it (backwards). And even with the wheel locked, it's nowhere near as stable as the 4 wheeler where I always have at least 2 wheels on the ground.
It probably doesn't help that my 3 wheeler (P&T) is twice the weight of my 4 wheeler (Maclaren Vogue). I live at the bottom of a hill so I have the choice of pulling the pram up a flight of stairs or pushing it up a huge hill to get to the shops. Neither of these is a pleasant experience with a heavy pram, especially when you are 5'2" and a P&T in double mode with two 10+kg kids in it weighs almost the same as you. I can carry the Maclaren, kid and all, up the stairs. It's the lesser of the two evils.
I'm not sure what options are out there now, my initial pram shopping was done 5 years ago and I couldn't get everything I wanted without taking out a loan. The prams in my price range that could face rearwards didn't steer very well in that mode, were heavy and hard to fold and didn't fold very small, so I ended up throwing in the towel on that requirement. My eldest was a ridiculously early talker so I don't think it afflicted her too badly.
Everyone in my neighbourhood probably thinks I'm a nutjob though because I did talk to my kids even when they weren't facing me. I've also been known to talk to them when they're not there. Uh huh. Nuts.
Best of luck OP, hope you find what you're looking for out there.