but does eany one knows the diferences betwen Bt and Alpha?
Alpha Black can fit a cyclone and/or egrip (as well as any M98 board), the stock can be removed without disassembling the marker. It has a 98 barrel thread.
I think the Omega can fit a Rip-Clip, but don't quote me on that. I think it has an A5/BT4 barrel thread, but, again, not too sure. AFAIK, it can't be fitted with an egrip. (haven't actually seen an Omega outside the internet, I don't think they've really taken off in the UK...)
Internals are practically identical though, so unless you intend to fit some of said gubbins, there's not a lot between them.