Well, I'm not going to the Messe, but I do have a Monke Bflat trumpet.
The Monkes have been good trumpets for ages and still are quite good. But, lately, there are some other manufacturers that build better rotary trumpets. Let me point out Lechner and Schagerl. Lechner has been around now for some years and replaced Monke in most trumpetcases over the years. The upcoming horn that is replacing that one is the Schagerl.
I had the chance of testing the Schagerls a bit a short while ago (I was playing the Götterdämmerung and the trumpet section I sat in was testing them).
I started playing the opera on my Monke Bflat, but after a week of rehearsals I had the chance of playing a Lechner C (I borrowed that one of the first trumpeter, he didn't need it anymore because of the new Schagerls). I didn't switch back anymore and decided to sell my Monke and buy the Lechner.
If I had to choose right now I would buy a Schagerl (if only I had the money). They are fantastic! I would go for the Vienna modell. Put a Breslmair mouthpiece on it and you're good to go. Absolutely fabulous!
As for the Monke piston trumpets: I don't have a clue!
Jeroen.