The outcrossing really depends on what you do and where you are too. If I were in an area where Saddlebreds were better known, I'd be way more likely to stay purebred than any outcross... But, in my area the breed is almost unknown, and while they might have the talent and ability of other breeds in any given discipline, they are a hard sell as a purebred.
I had a lovely gelding I just sold. This horse had eventer written all over him...trainers, coaches and other riders all agreed... But Trying to get those sport riders out to look at him without trying to quibble on price (a price any of them would have paid for an equal (or lesser) quality TB ) was impossible. In the end I sold him to a lady who just plain loved him for him, which, while I'm glad he is well loved... It's a shame in my mind, he could've done very very well in Pony Club, or even open divisions.
Interestingly enough, around me, Saddlebred crosses are "accepted"... Maybe because the buyers recognize the breed they are crossed with (especially the WB
So in the end it really depends a lot on what you need to expect from the foal... If it's for yourself, if it's for sale, which disicipline you want to ride, the level of the rider who will be riding the foal.... All those things factor in.
This year we will have one purebred mare and one Clydesdale mare bred - I expect both to be fabulous... But they will be different for discipline suitability, I am sure.