I'm keeping the TSR-8...
... I can wear out the cheaper machine instead of the expensive one, and that also means less passes on the final master tape.
Yeah...you save the 2" tape...but the multiple passes on the TSR-8 would still be "worn out", so transferring them to the 2" won't save that. IOW...you still end up with "worn" takes on the master tape.
I do lots and lots of passes of the tape with my MX-80, as I tend not to punch in, and so I retrack all the time....and there's not much wear that I've noticed. I think most of that happens with fresh virgin tape, in the first bunch of FW/RW/REC/PLAY passes.....after that the tape tends to "settle in" and from what I've seen, holds very well to lots of work. Also, the MX-80 transport is pretty smooth-n-easy, at least if it's running right.
I use mainly 499...and it just holds up.
The way I look at it is...I want all my tracks recorded on the best machine that I have....especially the main tracks, like vocals. If anything, I would use the TSR8 for any additional, less important tracks that I need to add, or for doing the "tape tricks" stuff before dumping to the 2"....or the DAW (not sure if you transfer all your stuff to a DAW at some point).
For me....it's mostly about KISS (Keep It Simple Stupid).
So while I could lock my Fostex G16 and the MX-80 all together, and lock both simultaneously to the DAW and all kinds of additional MIDI gear...etc...and have it all synchronized and playing the main tracks, the add-on tracks, the virtual tracks, etc...(which I've done in the past just to see how it all rocks together, and after awhile it gave me a headache doing all that
)...
...it's just so much more simpler and easier for my sessions to do all my tracking on the MX-80...and then whatever edits I need to do, I save for the DAW, where it's a simple cut/paste mouse click.
The tape deck...the MX-80...is just my main recorder that captures the audio for me. I don't use it or the tapes for anything else once I transfer to DAW....but I do keep the final reels with whatever filled up the tape, which are usually most of my main tracks. Any second passes/transfers to the DAW would only erase multiple takies...like I may do two takes of bass, then when I transfer the initial tracks to make room for a couple more beyond the 24...I'll erase one of the bass tracks....or two of the three vocal takes...etc....etc.
It's just my way of working...YMMV.....
Any idea if the heads are the same as on the MTR-90?
No...
I've thought of that too as there's been a couple of times that someone was selling an MTR-90 head stack (once just the other day for like $500).
I have a spare used head stack, but it came from a machine that was in some kind of fire/smoke situation. The machine didn't burn, but the soot from the fire was all over it. I bought a few audio cards and the head stack...dirty, but the audio cards work, so I assume the heads work too, they just need to be sent out for a polish and possible re-lap and block alignment.