I prefer Lagers by far. I'm not a fan of the buttery-ness of an Ale.
Butteryness is a flaw in most styles, ales included. There are a few that allow it (such as ordinary bitter, and mild), but even in all of those the idea is that it is limited to low or none. If all of your ales show butter (diacetyl), there may be something else going on, or you are exceptionally sensitive to it. I doubt the latter because in general, lager yeasts are far more diacetyl prone than ale yeasts. You'd find the lagers even more buttery (diacetyl rests included).
You may be rushing your ales more than your lagers, or perhaps you are allowing proper diacetyl reduction by following a stricter protocol when you ferment your lagers.
One other possible culprit is overuse of WLP002/Wyeast1968/S-04. This British strain is a diacetyl generator and beers brewed with it should get ramped temps at the end of fermentation in the spirit of a diacetyl rest to reduce it. You CAN brew diacetyl free beers with that strain, it just takes a bit of focused attention.
HTH-