A CB250/GA5/45K25 will handle any thread thickness you want up to 415 (maybe even 500 at a stretch)
Yes, the 441 clone is the ducks guts but it comes at a price.
When people come to me looking for a machine I start by looking at what they really need to do and their sewing experience. If they are just starting out and really don't know how much work they will eventually do then often I will suggest the GA5 route as an inexpensive way into the game. While most saddlers I know have a Pearson 6 or a 441 clone they all have a 45k25 in the workshop that gets used on a regular basis it isn't as if it will be wasted. On the other hand, if it has been been set up properly from day one, it will always have a good resale value.
A flat bed has a lot of limitations but a cylinder bed can always be fitted with a flat bed attachment - even if you make it out of plywood.
Just my 2 cents worth.