I'm assuming that you are just talking about hogging material out of mortises? I have the Makita chain mortiser, and a boring machine. I like the control of each. Makita has settings before you plunge, and a boring machine is pretty consistent if you start the bit correctly. I would not hesitate to use the boring machine if I was working with someone and they were using the Makita. Many at first think the boring machine is slower, but with experience, I'm not really sure about that. While it may plunge somewhat slower, it takes less time to reposition. It's not so noisy either, and many find it more enjoyable to use.
Now when it comes to drilling peg holes in a mortice, I definitely prefer the boring machine, because it will keep you drilling perpendicular. I like that, if your drill with stand keeps you perpendicular, great. One down side to the drill is that it is so fast that you can quickly blow out the other side. With the boring machine you can feel when your bit tip is poking through and stop before you blow out, flip the workpiece, and drill from the other side(probably with a bit an brace there) so that it leave you with a nice clean hole on that side too. If you are draw boring, you especially don't want to blow out the other side of your tenon, at least I don't, so I use the same technique with a brace and bit there. These old tools are great once you learn how to use them(and they must be sharp), and get some experience with them. Here's my boring machine. I think Jim Rogers told me it's a Snell. Got it through ebay for $125 or $175, can't remember which. Millers Falls is the top dog of boring machines, but not cheap. One day I'll get a millers falls, but this works fine.