I'm with UG on this topic. With a consistent set of F1 cows, a good hybrid bull will deliver a set of consistent, growthy calves and can be done more economically than using a purebred bull on those F1s.
As an example, I've found that my best calves are 25% Simm, 50% Shorthorn, 25% Angus. You can give or take a few percent on any of the breeds and still maintain consistency. The only way I could normally accomplish this is with Simm/Angus cows crossed to one of my purebred Shorthorns (I'm a PB Shorthorn breeder, just starting out). The issue is that I'm not a big fan of Simm/Angus cows, and prefer to have Shorthorn/Angus cows around (they keep easier, tend to be higher volume and closer to the ground). Crossing to a full Simm bull, I end up with calves that are a little too leggy, a little too slab sided, and keep a little harder, given the Simm genetics that are readily available to me in my area. However, I can use a Simm/Shorthorn cross bull, get my 3 way cross for maximum hybrid vigor, maintain consistency and increase fertility and longevity (not that I have trouble with the PB Shorthorn bulls).
Having said that, I've got some cows in the herd that were "experiments" or were simply too cheap to pass up. Either they're F2 cows with some Shorthorn in them already, or else I really don't know what they are because the original owner didn't know. I'd never even remotely consider using a hybrid on those animals, and they run with my purebred herd and bull.
Long and short of this ramble: If you know what your F1 cow herd is, a hybrid bull can help if selected carefully. If you've got cows with varying degrees of breeds, stick with a purebred.
Rod