Getting stuff into a suborbital trajectory is basically a subset of getting stuff into orbit. It's basically like, if you can drive from NYC to LA, you can drive from NYC to Chicago.
It could very well be that Virgin's chosen approach is more difficult because they are using airplanes instead of rockets. But nothing forced them to choose that approach, and it's not the mission. If you find it harder to get to Chicago than I do to get to LA because I'm driving a car and you're using a kayak, that doesn't mean your mission is harder.
Except a car costs $30,000 and a Kayak costs $300 with much lower running costs. Virgin are not trying to be the first to get into Space, they're trying to reduce the cost and make it more affordable.
Lower cost of access to space is SpaceX's big goal as well. So far they're doing much better at it. I wouldn't be surprised if SpaceX could meet Virgin's price for a suborbital trip, if they felt it was worth their while. But they have vastly larger fish to fry.
It could very well be that Virgin's chosen approach is more difficult because they are using airplanes instead of rockets. But nothing forced them to choose that approach, and it's not the mission. If you find it harder to get to Chicago than I do to get to LA because I'm driving a car and you're using a kayak, that doesn't mean your mission is harder.