My two cents is as follows; 1. Make sure the SPG you are using can accomodate modern tank pressures if you aren't diving vintage low pressure tanks. I have hooked up an old "Sea Vue" and killed it using a 3300 psi tank. 2. Go solid brass with a maintaninable bezel. replaceable o-ring/gasket and lens if possible. They are far more rugged when using a Banjo fittting. The plastic ones can get dinged, scratched or even cracked when whipping around on a lone hose off your yoke.
My favorites are Scubapro, or Farallon. USD did make an all metal one as well, but are harder to come by.
"Where'd ya get that ol' thang, don't cha' know them thare things ill kill ya!"
Live From the Red Sea,