I have a press for flowers and hash, but still prefer solvent extraction for pro. The people I know are using ice and dry ice methods for pre-hashing, or dry sift. As for press yields from quality material, my results are roughly close on par with BHO ratios (only stuff left in the rosin chips is low quality gunk, same as when over-extracting with solvents).
Just a thought, if you can taste a substantial difference between your raw bho and qwiso, then one wasn't processed or purged correctly. Properly winterized products taste better not worse, smoother with less contaminant and cuticle wax flavors, and less crap left to oxidize or go rancid as it ages. Also winterizing removes fine dust and dirt particles accumulated from the grow environment (not a small factor in my opinion, if quality is your goal). Of course a portion of the more volatile
terpenes are lost under vacuum, and longer vacuum is required for alcohols (or higher heat, another road to off flavors).
I've noticed some commersh and many home-made winterized oils aren't purged completely, and as a result have remaining alcohol/sugars/water. Longer soaks, freezer or not, extract more water-solubles. ETOH has a strong affinity for moisture and the commonly available 90-95% takes more purging time/effort than higher grades (re/distilling your own helps if on a budget). ISO works but has a much lower margin for complete purging, and any leftover solvent you miss is highly toxic (ETOH considerably less so).
