Hi CL,
I love all the watches in your selection in fact!
Still I may have preferences.
If we could consider it in the selection my favorite would be the 5020. It's a cushion case (like 5135) so not rectangular, but still a form watch! The 5124 and 5100 are not exactly rectangular either.
So 5020 first! Then the 5105 is a pure dream, but to be honest that's the one I've never seen in the flesh.
5100 in pink gold would come next, followed by the very affordable and really superb 5124.
5101 comes last but mainly because it's so expensive and you could perhaps get all all the others for the value of 5101! 
Regarding the calibre in 5124, for it's a form calibre, no matter if it's a 215PS reformed! It's bridge design is really pleasing my eyes and that's what counts! Yes I think it's a great calibre. The 5124G is IMO the best entry level PP today (close with the grey dial 6000 that I love too).
Cheers
Dje