Twin would be much nicer bike to use in my experience, lower centre of gravity & better power spread. Rode both on the road in my youth & the 350 twin was so much better in every way
The bike in the listing isn't a twin, just a twinport motor like all Jawa 250s. Wouldn't have a chance against a CZ but would still be a heap of fun to ride
Tank is 50s like dad's 350 twin, the hole in the centre is for the ignition switch/amp meter unit so I'm picking it's more suited to pre60 or 65 than pre70.