Which grading company should I go? I'm new

I have a Sylveon masterball 50/50 left/right, 60/40 for top/bottom, and Venusaur EX 50/50 left/right, 55/45 top/bottom. I wonder if either one can get BGS black? If not, should just go for PSA 10 or take the chance of CGC pristine? First time try to send card to grading, looking for some advise.