I have both, the belt sander and the nock and point jig.
the taper jig is great...though my belt sander stinks (older craftsmen model disc belt combo).
the nock and point game could be done on the disc. I also have a woodchuck and love it, use it for my points only though being I shoulder them and do my nocks on the tims jig. It does ok but no better then anything else and being you'll have a disc sander you could easily set up a jig to do the same thing. Imagine a much larger woodchuck on that disc. Make a plate to fit on the table and mount something to fit in the miter slot (screw the strip that fits down through the miter slot and then screw that hole contraption to the false table. Epoxy the bolt in the alignment strip for the miter slot so it doesnt turn and you can remove it with a simple nut on the bottom.
If you look at the tip and point taper jig it has this false table I'm talkign about already incorperated and another adjusting table on top of that so you can tweak the tapers.
The woodchuck does great for shouldering points and it's my dedicated 23/64ths point taper jig only.
reread this and didnt really clarify but I'd buy the shaft tapering jig again. I'd pass on the nock and point jig being you'll be able to homebrew one easy enough and you'll have the disc sander to do it on. Just to clarify