I owned a FOIS and it was great except it looks a bit too sterile...it is an homage to a 2998 but if you look at enough actual 2998s the FOIS starts to look "wrong". The lume is too white, the sapphire crystal is too milky, the logo is the modern one, etc. I prefer the 60th anniversary Speedy for those reasons. But if you don't follow vintage FOIS is a great and more affordable option.
I've never owned a DSOTM but I agree with your concerns about value, they sell well below MSRP and are slow movers on the pre-owned market. If it is going to be a keeper that shouldn't matter but something to keep in mind.