I was in almost the same situation as you. I was considering the brommie M series, the downtube mini and the curve. I ended up going with the brompton m. To me, the tight fold was paramount in my consideration as I will be taking it on trips. Thus, the brompton won. The folds in the others were somewhat messy. My brompton stays together just fine when folded.

Anyway, I will be posting pix of my new purchase soon. Stay tuned.