Not my experience with Uppa. Any problems have been dealt with well and in good time. We, the retailer deal with the manufacturer not the consumer, they've always been fine.
To be fair to Silver Cross though, they too deal with problems fairly quickly.
My issue with Silver Cross is that they seem to be a bit overpriced for the quality they deliver. They're not terrible, but (in my opinion anyway) they are trading on the top quality, luxury reputation of yesteryear. We have lots of misty-eyed grandparents-to-be come in and talk about the beautiful Silver Cross prams they owned and think they are buying the same type of thing, it's just the name. Yes, the Heritage coach built prams are as lovely as they ever were but the lifestyle stuff is just middling for top prices.
The Vista has pretty big wheels all round and are probably better than most 'small wheeled' systems when off road. It is important to lock the front wheels to the fixed position when walking on rougher surfaces. Maybe people don't do this?
The Pioneer is basically a Wayfarer with bigger wheels. It's probably much smoother than a Wayfarer due to the size of the wheels but the Wayfarer is very stiff and unforgiving on any surface so it's an improvement for sure.
Price wise, the Vista and Pioneer are pretty similar but (for me) the Vista represents better value for money with more features as standard (rain covers, bug nets, Maxi Cosi adapters, huge storage basket, UV sun shades built in).
Uppa Baby are just about to launch a few new colours which will be available in December but they are also increasing the price to £700, so if you go for this do v soon before the price hike!