You're right, no one needs to answer for his own taste, let alone justify his friends'.
And these reports are appreciated, even bad experiences. I would say,
particularly if they are bad experiences. It helps others like me make decisions.
It's been some time too since I stepped into Arena myself, nor have I seen reports from anywhere lately. Based on my last visit, I have the recollection that it was gently going to seed. Hence, I wouldn't suggest that its facilities are phenomenally classier than Sukothai Massage and that ilk. But there remains a difference nonetheless: Sukothai et al are foot massage and thai massage places, not sex massage places, therefore there is the extra hassle of having to negotiate for sex, which negotiation may not always be successful depending on the boy; whereas at places like Arena, the climax of the massage is expected to be, well, a climax. Showers are also ensuite in both Arena and Body Club.
Price-wise,
Arena is 450 baht for one hour,
Body Club is 395 baht for 90 minutes, comparable to what your friends are paying at those "grungy" and "grotty" (theoretically) non-sex massage places.
But I do understand that sometimes one goes to the mangiest dog of a place in search of the one love.
We've all done that, I'm sure.