Depends what you do.
Fixed power lenses are the most rugged, and have the best optical quality if you're comparing apples to apples.
I don't have alot of experience with riflescopes, but I'm an avid photographer, it was my university arts minor, and I now run a darkroom, and fixed power optics always deliver vastly superior optical quality. For example, Canon's currently made 50mm f1.8 that sells for about 90 bucks, delivers better optics than any zoom they make under 1500 dollars, although it is not as durable as their fixed power 50mm f1.4 that sells for about $300, and blows away just about any variable power canon makes, including alot of L series lenses.
Also, variable magnification lenses of extremely high quality are being made that exceeds the reproduction value of newspapers, and most magazines. The same advances that allow variable magnification lenses to have become better, have allowed fixed lenses to become much better also, so fixed lenses are still the best, but unless you are going to reproduce the photograph, as an actual photographic print or in the highest quality magazine, then the extra optical value is just wasted.
None of this matters though, if you are the type of person who uses the same rifle for all sorts of things, and might hunt deer at close range one day, and groundhogs at 250 yards another day. It's hard to find a single magnification that suits every circumstance. With photography, we just switch lenses, or cameras. That's why you see pro photographers with two or three (or seven) cameras hanging around their necks.
**Please note** I'm not trying to say that you can buy some cheapo chinese fixed power scope, and it will rival the optical quality of the finest quality variable power scopes. That would be comparing apples to oranges.