If we're looking at opportunities - the mainstream market is less mature, has less restrictions and is WAAAAY bigger. It is difficult to measure the actual size of online porn, but I've seen sources that estimate it's between $5 billion and $20 billion a year. Ecommerce is a little easier to measure and Statista says it's $1.5 TRILLION. (
E-commerce worldwide - Statistics & Facts | Statista)
Considering the market is less mature, that sounds like a whole bunch of opportunity to me! The shear size of the market makes it more attractive. Online porn only appeals to a portion of the online audience (mostly dudes although more women are clicking on, it's still mostly dudes). But it's not all dudes, I've seen estimates between 60% to 70% of dudes and 15% to 20% of ladies enjoy smut. Compare to 90% of both men and women having made an online purchase...
Bigger market, bigger opportunity. Assuming the barrier to entry is the same, I suggest using the lessons learned in adult and taking advantage of the mainstream industry ;)