Try them.
If you have a good transmission, it "locks" in the extended position, so the refill won't creep back into the pen, as you write.
If you have a good "nib", it will not bend easily as you assemble the pen.
There is no way to know by looking, if you have crappy plating--but it will show up, over time. Best way to avoid it is to buy from resellers you trust.
Another potential problem: the fit between the upper tube and the transmission--again, this is more of a "hit and miss" problem and can be corrected, but it is a sign of less than careful quality control by the manufacturer.
Find the one you like--the pen you make reflects on YOU, and none of these kits are "pricey" if you buy in any quantity.
Oh, and my personal OPINION!!!: None of them write nearly as well as a Parker mech with a Schmidt 9000 refill, so I would avoid them all as much as possible. Having said that, I am "commissioned" to make one for my granddaughter and I certainly WILL. At age 10, she is not a discriminating buyer---we will fix that by the time she is in her teens!!:biggrin::biggrin::biggrin:
FWIW,
Ed