I have both a 1541S clone (with the dual pretension assembly from a 1508 which enables my 1541 to tension #207 and #277 top & bottom) and a Portable Walking Foot
the Portable is a great Binding Station and the true value in it is in being a Walking Foot Zig Zag. That is just a unique value in and of itself. I see the Portable as more-so a complimentary machine to pair alongside a dedicated compound feed like a 1541/206Rb/111w etc etc.
the later 1541's are quite possibly the best compound feed machines in their respective class. I've sewn on the newer pneumatic 869's and LU-2810's and I didn't necessarily prefer them over the 1541. They are more "featured" machines sure, but they all completed tasks to the same degree. If there is something a 1541/1508 cannot sew it's time to get a 441 Class machine. Like I said mine has the dual tension assembly from the 1508N, most of the JUKI models only have the single tension pre-tension unit.
Sailrite's Portable is nice, the metal tolerances are better and you can truthfully swap their parts into a REX/TUFFSEW/OmegaSew/Sewline etc etc. I'm in process of adding Posi-Pin to mine. There is utility in the Portable Walking Foot but it will need another $300-$600 to be machine-hacked into being useful. I think it's best as a complimentary machine though.