Mountain Lion is the only version of OS X which I don't have experience(I'm serious about that-I have a computer loaded public beta and then 10.0-10.5, along with another loaded with all four developer previews plus Rhapsody and OS X Server 1.0v3). The only thing I've done in it is boot into single user mode on my BIL's Unibody Macbook to change the password(he bought it used and didn't get the password with it).
With that said, Lion was the first version of OS X which I used extensively. A lot of folks complain about "iOSification" in it, although admittedly it didn't bother me a lot, but after using older versions(Leopard is probably the one with which I have the most experience) I can certainly understand it. After using Leopard a LOT and Tiger quite a bit, I've gotten into the habit of going into finder or using Spotlight to launch apps rather than using Launchpad.
In any case, I currently have two computers running Lion. One is a polycarbonate iMac, and the other a black Macbook. Lion is the "end of the line" for these computers. I also have two running Mavericks-a 13" late '11 MBP, and an 15" early '08 MBP.
Mavericks is great on these computers. IMO, the iOS-like features have been polished to the point where they really not that intrusive, but IMO quite convenient. As an example, if you have an iPhone and receive a new iMessage, it shows up in a pop-up in the upper right hand corner of the screen, and you can either ignore it or reply just by clicking on the box. Mail works similarly. I've heard some complaints about it. One of my friends in the PPC forum says that the restructuring of tags has really hurt the workflow they use at their office(in earlier versions of OS X, the entire file/folder name was highlighted in color, while Mavericks and Yosemite use a small colored dot next to the name).
My 13" has 8gb of RAM, while my 15" has 6gb. Both have platter drives, although the one in the 15" is a hybrid drive(small SSD+big platter drive). When I installed the new HDD in the 15"(it was sold to me as having a failing HDD) I actually cloned the drive in my MBP, so effectively the two computers are set up the same. I find Mavericks to be pleasantly useable in both computers.
Mavericks is going to remain my preferred version of OS X on computers which can support it for a while-probably at least as long as it continues to receive security updates.
I have a white Macbook running Yosemite(mid-09, pre-Unibody). It has a cheap 256gb SSD(lightly used computer with SATA I, so I didn't see any point in buying a high end drive for it). Yosemite flies on it and I also like some of the new features it offers. I can't stand the flat UI, though(personal preference) so have not installed it on anything else. I actually bought that Macbook(cheap) in the Public Beta period with the sole intention of installing Yosemite. I have no performance complaints whatsoever, and even like the wallpapers enough that I'm using them on several older versions of OS X(on a casual glance, Tiger actually looks like Yosemite if using a Yosemite wallpaper, although the pinstriped dock and blue Apple give it away pretty quickly). I did see a noticeable speed improvement, however, when I went from the factory platter drive to an SSD(remember that I'm running Mavericks on a platter drive with a similar Core2Duo processor). I really think that you need an SSD to see the full potential of it.
As far as battery life-I've noticed little difference when changing OS versions on one computer.
I can't speak to Logic Pro, but have run CS6 on 10.7, 10.9, and 10.10(it was installed on my Macbook when I bought it). It runs great on all. That same Macbook has a version of Logic Pro installed(not sure what version-I never use it) and will test it in 10.10 when I get the chance.
