I understand how you feel @DaveP. It took me a long time to bite the bullet and move my domains from elsewhere. I was doing OK elsewhere and making a nice income, so it was a brave move as SH was unproven at that time.
I moved my domains when there was only around 5,000 domains in SH marketplace and I capitalized on that. I think I’ve done better by moving, but I don’t know if it’s because I got in early or if I really have done better, I’ve had to drop my prices by at least 40% to get them approved here so I needed more sales just to keep the income I was getting elsewhere and I’ve not moved the more valuable domains here as I’m not prepared to drop my prices on those. I honestly don’t know how I’d feel about moving if it was now so I can’t help you in that area.
Perhaps you could list new purchases here and build up a new portfolio then you can compare how you are doing at each marketplace and move to the one that fits you and your domains the best.
Whatever you decide, good luck!