to me, it's hit or miss. Depends on the girls, and if they're comfy with eachother. I've had bad sessions, it didn't feel worth it.
In pr0n, it looks great when there's 2 girls, but they are being directed. So, you might have to do a little directing because it feels unbalanced when they're not in sync. Both massage and flip. Like above, they both have their own style. So having your leg pressed hard and fast, and having your arm kneeded slow and soft, it's weird, imo.
But if you get 2 girls who are friends and can be in sync, it definitely makes things more fun and interesting. There could be times where you don't know where to direct your attention, cuz there's so much going on lol it's fine when they're both licking your balls. But who do you look at when both are licking each nipple? Then you start to play with their pussies at the same time? It can literally double the experience.
also if they're friends, you don't have to worry about "parlour drama". it really breaks the ice overall, and you get more of their real fun personalities. Its just kinda liberating that everyone is on the same page: you're there for a massage, they get money, and they both just want you to bust. They're both encouraging and feed off eachother, and everyone's having a good time.