I would just say the 5170 is a compeltly different watch: it plays a classical and more dressy role, thus it is less interesting if we prefer watches with more character.
A simpler watch will always have more difficulties in appealing to someone.
As for the 5970/5270 topic, I agree they are much closer. I saw the 5270R lately and loved th edial.
The only thing is that the 5970 has this little "old" or "authentic" look which makes its charm.
As you are, I can't choose right now which one I would pick. I have to try them several times first.
However, I'm also quite attreacted by the 3970... hard to decide. I'll make a post to have the impressions of 3970 owners.
Thanks for the 2 pictures, I try to gather as much as I can so if you have more of 5070/5970/5270, I'll be very happy 
Thanks for your input Bruno.
Cheers, Mark