Ugh! And you were doing so well!
First there is no Fostex version of the TSR-8 or even 38. The Fostex 8-track offerings were always on 1/4" tape.
Fostex was started by former Tascam engineers, but it had nothing to do with a spat over design issues. It was purely a business venture. Though what you are saying was part of the pitch by music store salesmen at the time.
I was there when Fostex introduced their answer to the Tascam portastudio and their first 8-track 1/4" reel. It was just terrible compared to Tascam. I had a good friend that took out a loan and built a studio with the original Fostex 8-track, half-track, and companion mixing board. My Tascam 244 cassette portastudio ran circles around it. He was very disappointed and sold it at a loss after a few months.
Fostex actually made the first salvo ever toward cutting costs and cutting corners in the portastudio wars. They are solely responsible for lowering the bar and the flood of toy-grade portable studios that followed. It wasn't pretty.
Back then we looked at Fostex as better than nothing if you couldn't afford Tascam.
Fostex quality did improve and they went a long way to redeem themselves as the 1/2" 16-track format matured. They beat Tascam to the punch by releasing the B-16 and E-16 before Tascam got around to the MSR-16.
The Fostex and Tascam 16's are both very close in quality. Tascam still gets the nod from me at this point in time because of service and parts availability.
Fostex support has virtually disappeared for their analog lines. There are a few common, fatal flaws in the Fostex units that can't even be repaired for lack of parts.
Some of the choice comes down to whether you have a preference for Tascam dbx or Fostex dolby C. The MSR and E units with dolby SR are pretty evenly matched in sound quality.
The E/G-16 is a great machine. Tascam came from behind with 16 on 1/2" but ultimately trumped Fostex with the MSR-16. That would be my first choice, with the E/G-16 a close second.
-Tim