Not familiar with these models, so I'm not sure that a GW690 would be more reliable or not. I've not known anyone who's owned them.
Unfortunately I've had bad experiences recently, I got 3 dud cameras in the last two weeks. Mamiya 645E DOA, Praktica LTL3 broken frame spacing (unusable), and Vitomatic II with heavy oil in the lens.
I tried to work with the sellers but they are really dragging their feet on the refund, so I requested a return, and they are dragging their feet on the return now.
Hopefully I will get my money back eventually but it has been a pain dealer with these ebay sellers. I'm wondering if some people are getting desperate and not having enough money to issue refunds with the economy as it is now, or trying to risk selling broken/untested stuff.
It's quite strange to have zero duds in 2 years, and 3 in a row at the same time.
I ordered a Minolta 35mm to replace them, I've never had a broken Minolta so I think I'll stick to them for the time being.
We will see but personally I'm going to hold off buying an expensive medium format until the economy improves a little bit, but I might have been unlucky and YMMV, the decision is up to you.
I think some companies electronics seem to last the test of time better than others.
I've bought my fair share of second hand cameras, and I've yet to have a bad electronic Nikon camera for example (it also helps that they're cheap and low risk). On the other hand I'd have significant qualms about sinking money into Yashica/Contax electronics.
If I did buy a GA645, I'll be buying from a Japanese eBay seller without being able to check the camera over as there's not much chance of buying one in the UK.
Hence some reticence to pay £600-£800 on an unknown quantity.
I may just plump for a GW690 series if they're more reliable?