I'd personally always put condition and documented history before mileage.
And 25k? It's nothing. It shouldn't really be any worse a car than one of the same age that'd done 15k. In fact, assuming the 25k car is in good nick, you could probably find plenty of lower mileage cars in worse condition.
When you get up into the 100k mark (for argument's sake) then naturally there are more considerations when you're looking for one - belt changes, clutches etc - but at 25k it theoretically won't need anything big for a long time. Therefore you're in a good position in terms of being able to judge a car more or less at face value, ie its general condition.
The best thing to do is just get out there and see as many as you can in the flesh. So many of the cars that tick the boxes on paper turn out to be a bit rougher than the ad suggests!