Well, I have probably 20 scopes and 4 or 5 are fixed power, but they're my favorites. Less lenses to look through, less complicated, and no shrinking reticle as in FFP scopes. I have Two SWFA SS scopes in 10X and 12X, one Optisan 10X, one Hawke 10X, and a Veyron 10X. I haven't found my holy grail for hunting, a 6X AO, but I'm looking.
It seems like in a scope line, such as Hawke Airmax or Vector Veyron, the glass in a fixed scope is just a bit better than the variable scopes in the line. I'm guessing it's because there are less lenses needed and that helps clarity. Both my Airmax and Veyron are a bit clearer than their counterparts. Also, I'm used to taking my variables to a certain power and leaving them there. If it's a SFP scope, i usually leave them at whatever the reticle is calibrated for.