In a recent FWW tool guide, they gave a very good review to the Delta
14-651. (Tops were General International and Woodtek, in that order...both very substantially more expensive.)I just bought one last night on Amazon...they had it on sale for $199, and with the $20-off promo, that brought it in at $179, with free delivery to boot. For that money, I couldn't say no. (Woodcraft sells the same machine for $269.)
I just looked, and the price has risen to $229, but that now qualifies for the $40-off promo, so your delivered cost is just $10 more.
I (obviously) haven't used the tool yet, nor any other mortiser, so can't answer you about which is the best model, other than based on a single review.
But I sure as ^%$# can't wait to get mine. It comes with four chisels as well, which I figure are probably crap chisels too, but an _excellent_ opportunity for me to learn to sharpen them, probably burn the &^%$ out of them, then throw them away and get better quality once I've gotten over the learning curve.