I own a Wessex Dolce silver plated (without trigger) and are quite happy with it. I bought it used, and it did serve me well. Intonation is pretty OK, sound is fine, response is good.
For a thorough study on intonation, check out
http://www.dwerden.com/Intonation/, I find this chart describing the intonation of the instrument faithful. My model has the same tendencies, I find especially B (24) to low, it seems a bit overcompensated on my instrument.
Probably I would like to have the Dolce with trigger to be able to lower the B 123 when I need a sharper version of B than my 24 gives.
I have test-played a used Yamaha 642 (before NEO model, 15 years old) recently because I considered an upgrade, but found that the swap was not worth the surplus money. The Wessex Dolce plays as well as the pre-NEO in my humble opinion.
I did test play a used Yamaha NEO (5 years old), which I find a better instrument than the Dolce, but at a much higher price range, so I did keep my Wessex.
Valves do operate fine, sound is great, and it does serve my amateur needs well.
My model has two smaller technical flaws - silver plating at one place was patchy, and 2nd compensating tuning bow sits too loose. The first I ignore, and the other was easy to fix.
I addition, I can assure that Wessex has great customer service, and does take customer satisfaction serious. I had no problems with warranty issues at my first Danube Eb tuba (which I bought new), and got a warranty swap.
I see that Wessex instruments technically quality keeps improving, hardening of bells is better now, silver plating finish is higher, and intonation better than just 5 years ago. Therefore I will not hesitate to buy another instrument from Wessex.
I can't comment on the other horn you are investigating.
Good luck, and please tell us your findings when you decide to buy.