Don, I prefer real tennons, just because i am set up for it already. but I certainly see the benefit of loose tennons.
- You dont have to figure for the length of your tennon when cutting lengths.
- You can lay out your pieces and check for fit even before cutting the joints, since the pieces wont overlap.
-You dont have to worry about getting a perfect tennon shoulder, which was the hardest part for me to learn. it is just a flat cut!
-Mortising may be the more difficult process, or at least the one requiring specialized machines, or a lot of chisel work. but if you have the machine, it is still only one process to set up. One hard process is still easier than a hard one plus an easier one.
Agallant, since you are asking, I assume you have not tried either method, and probably do not have a hollow chisel mortiser, or loose tennon mortiser, or tennoning jig for the TS. A loose tennon setup will be cheaper than both mortise and tennon, but if you dont have real plans of doing a lot of m+t in the future, I would suggest hand cutting mortises and tennons, you probably already have a saw, drill press and chisels. I have been doing it for years when I dont have access to my buddy's mortiser. I really enjoy the chisel work, and once you do a few, it really becomes a quick process.
I drill a line of holes with a forstener bit for my mortise, then chisel it out. Tennons, I just cut the shoulder on my TS, then split off the bulk and shave it down with a sharp chisel. done! For a beginner at this, I like to remind that hardly any of it is visible. As long as your shoulder is flat, and you cut your tennon a bit short so it doesnt bottom out, it will look perfect. and as long as you use a good glue, you can really fill a loose joint and get plenty of strength for most applications.
Plus, I find that learning to hand cut any joint, even if you plan on using jigs and power tools in the future, teaches you a lot about how it works, which surfaces really matter to the fit, and how to troubleshoot fitting it later when you set up your machines.
In the end, I think it depends mostly on what tools you have, or want to purchase. Either way, your joints will be just as strong.