Batteries? Hmm.
I have to confess, for several decades I've preferred mechanical shutters that will work without batteries, because I've been a bit obsessive about being caught out somewhere important with a dead battery.
But you know what? In nearly 40 years, I've never been stuck with dead batteries. Almost all of my cameras have taken small mercury batteries or LR44/SR44 batteries, and I've always had several of them in my bag. (The closest I've been to a problem was when I was living in Thailand in the eighties with my Spotmatic, and I realised I was down to my last battery - and mercury batteries were getting hard to find. But even then, I found a seller in Singapore about 6 months before the battery I was using failed).
R4A or R4M? I've got an R4A and an R3A, and I went for the A models largely because I really quite like having the choice. I like having the AE metering (The Rs and an Olympus OM2), but I also like manual metering (M6, OM1), and meterless cameras (M2, FSU cameras, etc) - I just like the different mindsets and thought processes that go with the various approaches.
So I'd say don't worry about dead batteries, and instead choose the kind of metering options that you personally prefer - and buy your batteries 10 at a time and always have a couple of spares in your bag.