If money is no object then go for it, personally having had about half a dozen duos over the years in these times I would rather have 2 separate punts for the same amount of money.
As has been said, if you do go ahead do your homework & make sure you pick the right girls
I agree. Two separate punts for the same money is better for me. With two girls at a time, somehow I find my concentration is divided with the result that the satisfaction I get is diluted and less intense. Maybe I've never quite found the right girls. Everyone seems to agree that finding the right pair is crucial. But I reckon right pairs are almost as scarce as hens' teeth.
And you're usually paying out double or close to double what you'd pay for the same amount of time with one girl. That's ok if you're loaded. But I can only afford to punt once every three weeks or so and I'm reluctant to splurge six weeks worth of punting funds on one encounter which, experience tells me, is likely to be a bit disappointing.
But if a MFF threesome is something you've always fantasised about, you might as well go ahead and have one. At least you'll have ticked one more punting box.
A MMF threesome or better still, a MMFF foursome, is something else altogether. If you're with the right people and everyone gets stuck in with equal enthusiasm, you can have an amazing time. I know that some on here will accuse me of being gay and that nothing I say will alter their view - to which, of course, they are fully entitled. For what it's worth, I'm not gay. Almost all my punting is with women. But I'm sufficiently bisexual to have enjoyed MMF, MMFF and also encounters with some particularly delightful TS girls.