Good grouping. I would expect the porro to be in that lot (note how it costs between double and a four times the other roofs!).
I mentioned star testing because I find it very effective for distinguishing the quality of bins. Much easier than terrestrial testing for determining sharpness across the field, field curvature, aberrations, distortion and transmission.
For example, the Winchester I bought from you shows some clear aberration in one barrel (the left, the one I can easily see the roof edge in) whereas the other barrel (where I can't see the roof edge) is rather better Jupiter disk image. It's the only bin I have that has a noticeably barrel to barrel difference. It's not obviously visible in terrestrial viewing but that's not to say it doesn't have some effect especially on small or detailed targets. And it says something about Chinese bin construction in 2005 when that bins was made: there was some variation in the quality of the components (the prism in this case). Note: I'm not complaining - they're fine for the price - they're just a nice example of seeing something in a Jupiter disk or star test that is difficult to see elsewhere.
The viewing of stars, Jovian moons and Jupiter's disk can separate bins into different classes (though you need each one to see the effect). The Jovian moons are very useful as they change their configuration so you get close "binary" pairs and dim moon closer to Jupiter's disk depending on your timing. I use this page to figure out what should be there!
http://www.skyandtelescope.com/observing/objects/javascript/jupiter
I find with these tests the bins I have fall into three distinct groups for image quality (sharpness, transmission and aberations):
porros (Yosemite, Celestron Ultima DX, Eagle Optics Raptor 10x40, Bushnell compact 8x26)
phase-coated roofs (OK one PC roof: the Vortex Diamondback 8x42)
roofs without phase coating (Winchester VDT 8x32 and the Promaster Infinity 7x32)
You can bird with all of them but some are better than others.
The tests are not difficult to do. Jupiter is bright (and conveniently located in the southern sky in mid evening right now). Just look at the objects with the bin. Write down what you see. It takes a couple of minutes per bin. Compare a group of bins and you get a feel of the differences.
Reviews on the Promaster Infinity 7x32, Eagle Optics Raptor 10x40 and Bushnell compact 8x26 are currently being written!