My suggestion pick one and send the majority of your high risk deals to them. Which one to pick? Whichever one you have the best relationship with, whoever has the most helpful ISO rep that you deal with.
Because as Allen said above, your relationship with the lender is very important, the more deals you can send a lender and more biz you do with one lender, the more corners they will cut for you. And if you have a good ISO rep that fights for your approvals for you, that can help a lot too
If you don't do a ton of business you may be better off going through a large ISO, they will know the best place to submit the deals to, your commissions will be the same as if you went to the funder directly, and you will probably get stronger approvals .