When considering frozen I almost always place the recent experience of other mare owners above all else. Talk to others who have used the frozen semen, find out the dates they used it and when it was frozen (if possible), as well as what, if anything, they did to get a pregnancy. Talk to mare owners with a good deal of experience if you can. Sometimes "tried and true" frozen stallions can have an abrupt change in pregnancy rates. It really pays to do your homework on the specific stallion(s) you're thinking of using.
......or you can have 80% motility, use the best vets and still not get pregnant the first time.
What I have noticed is that frozen can get really expensive really fast if they don't catch first time. This is even with the LFG that sometimes comes with frozen.
I'd say I was scared off frozen after last season's vet bills.