I have a pair of M-130's and you can't go wrong with them. They are also very sturdy mikes and can withstand a lot of sound pressure.
The tone is on the " dark" side and they don't have the sexiness and luscious sound of, to compare with something i know, and RCA 44 or bk-5. The back sounds exactly the same as front.
The M 160 is the Hiper brother and it seems slightly more open on mids while M 130 does not really make you any gift.
You still can make and Hyper pattern from M 130 covering the back with i.e. a pop filter or
a piece of foam at certain distance.
The bi-directional pattern is more versatile in my opininon and offer you a wider range of playng around.
I never had the pleasure of tryng a Royer, assuming you are talking about the R-121, but from what i hear and read you really should not go wrong with it. Also, as you probably know, the back is a little bit brighter than front so you are given the chance of suiting the tone for the application. In the same range i would check also
Mr. Coles...
Other considerations are what you are going to use
the mike/s for( that can lead to decide for Hyper or 8, Blumlein in your mind ??) and of course your budget. Two Beyers are less than 1 Royer/Coles.
An high quality preamp with a lot of gain is part of the deal...
Hope this can be a little bit of help. Jo

I use a Beyer 160 on my sax and for fiddle when I record acoustic bluegrass. It is a very warm mic and lacks the harshness I get when I use any other dynamic.

I haven't tried the other ribbons, but I have read nothing but good about the Royer's. I've had the Beyer for years and I love it.

I just realized I put the wrong number on that last post. I have a Beyer M260 not 160. Sorry about that..engage brain before fingers.