If you are going to get a GBBR, think about the availability of upgrade/replacement parts. Most likely, you are going to have to replace parts such as the trigger group, hammer, bolt, nozzle, bolt carrier, etc.
WE is a great platform because of the availability of parts IN country. You won't have to spend much time or money to get your hands on quality parts.
WA has very few parts, you will end up having to order from outside the country. Shipping costs can get quite high, of the $1000 I just spent on parts, I think I spent around $100-120 in just shipping. Duties on top of that will only add more.