It's important to note that not all recaros are the same. I've sat in both the GT500 Recaros and the CTS-V recaros and the mustangs were more comfortable. However compared to my stock Z seats they weren't.
Yes weight is one thing and no we have no specs on the seats weight yet. The other main attraction to recaros is that (depending on the design) you can quickly add a 5 point harness if you plan to do some serious tracking of the car.
I would revisit your question when the 14s actually hit showrooms. I know for me I'm not ordering them until I sit in either a SS/ZL1/Z28 that is equipped with them.
Hope that helps.
FOR SALE: 2013 ZL1 Message me if interested