NS4-H2 = USA made bolt on.
Euro = Czhek made neck through.
Forte= USA made neck through, stripped down.
I would put the NS4-H2 at the top of the list because they are closest to the top of the line Spectors, just in a bolt on version. Woods, electronics, options are all top of the line.
Forte would be next. No options for anything, but it comes in any color you want as long as it's black! Construction is the same as any USA Spector.
Euro is an overseas made version of the NS-2.
Personally I don't think you can go wrong with any of them, but the USA Bolt On's are my favorite Spectors ever. Here are my two:
The 4 string may be for sale. I don't know yet.