Economy Binoviewers: Which Ones?

I'm intrigued by binoviewers, though not to the point of spending more
on them than I did on the scope I'll use them with. In the economy class
choices seem to be:

o Williams Optics
o Burgess
o Stellarvue
o Siebert

Of these, and perhaps others in the $200-300 range, what are the pros
and cons including clear aperture, EP mounting (e.g., compression
rings), performance, build, included EPs/barlows, etc.?

I' do have SV and WO scopes and so far I've been happy with both
companies. The other two are not well known to me. And WO is driving
distance .. if there are problems.

Any recommendations? And why? The comparative reviews I've found seem to
be at the higher end of the price spectrum.

Phil