[_ck_]

Unfortunately bbPress version is extremely different to determine, however the point is moot as there are technically only two now, no?

Very few people still using 0.8.x unless they have hacked the core and they are stuck.

Personally I am waiting for 5.3.0 to be final and stable before going to 5.x

Until then, 5.x is slower than 4.4.x