As others have already pointed out, 350s with the UCE engine are not even sold here in the States. This may be because they were able to sell very few of the old 350 Iron Cylinder models back when they were made available here in the '90s along with the 500s. The vast majority of folks opted for the bigger engine, leaving the 350s to gather cobwebs in showrooms until basically cast off by the dealerships at fire sale prices.
That said, the 350 Classic has its own virtues if you don't mind taking the hit in power. For one thing, it's carburetted, so has less to go wrong. Gravity always works. I have one of the old "Iron Belly" pre-unit model 500s, but it has not escaped my notice that tales of various fuel system problems with the EFI seem to predominate in this forum. The fact that many choose to "upgrade" their EFI to an Amal or other carb, and that Hitchcocks in England sells popular kits for this might tell you something.
The 350s are also less "stressed" by the harsh laws of physics. Less stress will generally result in greater and longer reliability. That said, I think I might miss that moderately torquey "Oompf!" of a 500. But then, I had grown used to the full-on galloping Mongol horde tree stump pulling haul of Norton 750 twins. That said, given my ultra-sedate riding style born of decades of nursing old junk down the road, always giving our Interstate highways a wide berth, I could happily thump around on a 350 Classic. Sure I could.
I expect that your satisfaction with your choice will much depend on your temperament, riding style and the type of roads you're likeliest to travel. Personally, I thoroughly enjoy the mild and pleasant vibes of my old 500. Maybe I just got a good one, since the whole matter of vibes seems to be one of luck of the draw, but I wouldn't bother to so much as turn a screw to reduce them, let alone fuss around with mounting various vibe reduction gear like Carberry anti-vibe plates or bar-end weights as some do. I can see everything just fine in my stock mirrors at all speeds, thank you.
I suppose one could sketch out a 350 vs. 500 decision making flow chart. Here are a few criteria one might find in it:
- Is fuel mileage or cost to own, operate and insure a major factor? Have you ever used a teabag more than once? [If yes, 350]
- Are power and top speed important to you? Has a judge or prosecuting attorney ever characterized you as a "menace"? [If yes, then maybe a 650 twin's for you]
- Do the roads you are likeliest to travel have speed limits in kilometers per hour less than the average IQ of members of the British Cabinet? (or just Boris Johnson in miles per hour)? [If yes, 350]
- Have you ever said, "Hold my beer and watch this."? [if yes, then 500]
Others here far more knowledgeable than I about the UCE breed may have additional suggestions for determining an optimal decision matrix for the utility of the various models to best suit one's temperament and requirements. In the meantime, you might enjoy "H Sam's" YouTube offering titled,
Royal Enfield Classic 350 in-depth review & Why I bought the Classic 350 instead of the Classic 500