I have the Delta mortiser and love it. I looked a little at other brands but was in a bit of a hurry when I bought the Delta so that research was limited.
Since getting it I have used it a lot, with the original chisels, and have had no problems at all. I've used it on everything from pressure treated pine to oak and it works great in all of them.
I have a little more info on it on my site if that might help. http://www.newwoodworker.com/deltamorsmach.html
I think you should take a good look at the other majors, like Jet and Finch(?) as they are probably fine machines as well.
I have the Jet bench top mortiser and am very happy with it. I have used it in mainly red oak using the 3/8 and 1/2 origional equipment bits and had no problems with them, of course I have nothing to compare to since it is the only one I have used.
I got one for Christmas and have already managed to put it to work... what a dream to use! I have the Delta, which is very similar to the Jet, and think these 2 machines are the best value because they include chisels in addition to working very well. Chisels aren't cheap ($140 for a set of Fisch chisels/bits), and while the included set isn't top quality, it will get the job done.
There are 2 kinds of benchtop machines, slow speed units spin the bit at about 1,700 rpm while the high speed units are at 3,400. Record and Shop Fox are the only 2 high speed units that I know of, the other mfgs use slow speed motors. High speed gets the job done faster, but generates more heat on the bit which results in faster wear.
The Shop Fox machine is noteworthy because the depths that you can mortise to with this machine are simply unmatched. If you do heavy work, this would be the one to consider.
Back to the Delta and Jet models, the delta has a slighly smaller motor housing than the Jet, although I'm not real sure why because both motors spec out the same. Both machines have similar table setups, and they are easy to adjust. The chuck/chisel access is also the same, with the exception that the Jet has sprung metal doors, while the Delta has plastic doors.
Fisch also makes a mortising machine. Whatever you get, plan on bolting it to your work surface... there's a lot of leverage involved here.
The powermatic is about the best machine, but were talking 3 times the cost, the table and clamping system is by far the best.
I have the Delta, I was told, ( might be wrong on this ) that the chisles are different from the Jet to the Delta, and the aftermarket chisles fit the Delta, not the Jet, and being that I own both Delta and Jet equipment, I was really tossed up between the two, but when i found out the good UK made chisles were for Delta, I went with the Delta.
So after having the Delta for a while, and using the Delta chisles, I have been very happy with the Delta chisles, and dont see spending the high bucks on the UK made chisles any time soon.
One other note of caution, be careful with some of the high speed mortisers, i read a article that said they will burn the wood very easy, and what I found was, the Delta ( slow speed cutter, and Jet is the same speed ) cut pleny fast enough.
When you get a machine, go get yourself a couple of cone shape water stones for sharpening, I use these by hand, and sharpen the chisle from the inside, keep them sharp, and they will do a great job.
Is there a certain size of cones you should get? I have a diamond file for the outside of my chisels but have not gotten anything to keep the inner surface sharp. I have a Jet not a Delta but I was under the impression that they take the same bits.
You should NEVER sharpen the outside surface of a mortise chisle, your going to change the outside dimension of the chisle, and if you keep sharpening it that way, it will turn into a wedge shape chisle.
Hmmm, when I bought the Jet mortiser the guy (who does woodworking for a living) told me to take a diamond file and lay the chisel flat on it to get the burrs off the edges(which I could feel before I did this). Have I ruined them by doing that? I did it once on all four sides and now they feel very smooth. Perhaps I didn't use the correct terminology? BTW, thanks for the link...