I have had a Shoptask 1720 three-in-one since 1999 and have used it quite a bit. I bought it with an eye to CNC conversion and finished the conversion in 2007. My comments are based on my 20+ years of experience with that machine and the very limited info I've been able to gather about your two candidates.
Bolton: I found very little info online about that machine. Bolton has nine photos but only one shows the machine. The others are either the tooling that the machine comes with, or motor terminal block pictures that should be in the manual. Can't really tell much about the machine itself. Do you know if the head moves on the column (like some mini-mills) or if it has a fixed head with a quill?
Granite: I'm very surprised to see that the granite (which uses one motor for both spindles) is more expensive than the Midas (which has separate motors for each spindle). My machine is very much like the Midas. I've never used a one-motor machine but I'm pretty sure I would not like it.
So on to my thoughts and opinions:
These machines are called "3-in-1" meaning lathe, mill, and drill press. In reality, they can be decent lathes. As mills they are modest at best, and as drill presses they are terrible.
The reason they are terrible drill presses is the lack of Z travel. My machine has just barely over three inches of quill travel and no head travel. The Granite looks to be the same. Can't tell if the head on the Bolton moves or if it is also stuck with only quill travel. Think about the difference in length between a 1/2" drill bit in a chuck, a 1/16" drill bit in the same chuck, and a 1/4" end mill in a collet. Now think about how you are going to mount your work so that all three of those tools can be used with only 3" of quill travel. On a real drill press, you unlock the table, slide it up or down, and re-lock. Takes seconds. With these machines you are constantly messing around figuring out how to raise or lower your work. On a drill press where changing hole sizes should only take a few seconds this can be infuriating. You're going to need a full set of screw-machine length drills as well as jobber length drills because jobber length will be too long for big holes and screw-machine too short for small holes.
The milling function also suffers from the lack of Z travel. The only difference is that milling usually takes longer than drilling a hole, so the extended setup time is _slightly_ less frustrating than it would be for drilling. But compared to a mill with either a knee or a movable head you will still find it very slow and frustrating.
The other problem with milling is that milling needs more rigidity then drilling. That's why a drill press can get away with a simple and easily raised/lowered table. The milling heads on these machines are NOT rigid. Add in the tool extensions or crazy fixturing that you need to bring the work up to the quill and it gets worse. So you find yourself taking lots of light cuts. I can live with that now because I have CNC and I can program it to take lots of light cuts. But if you are running manually it will suck.
Finally, the lathe function isn't bad. Both of these machines look like they have traditional lathe carriages with rack-and-pinion feed for turning and half-nuts for threading. That is probably good (at least for lathe work). My machine has a permanently engaged lead-screw nut, which is good for CNC and for milling, but a bit annoying for lathe work. Before the CNC conversion I only cut a couple of threads in seven years - it's just a pain in the rear. (Of course, after CNC conversion is another story - any pitch, left hand or right hand, no change gears and no problem.)
As an indication of how well (or badly) these machines work in their various modes:
Within a year of buying my machine I found a Clausing drill press and almost never drill holes on the shoptask. When doing a CNC project, I'll use a short spotting drill to locate the holes relative to other features on the part, then take the part out of the machine and finish the holes on the drill press.
After about two years, I found a Van Norman #12 milling machine. Unlike the shoptask, I couldn't get it down into my basement, so it lives in the garage and I fight the seasonal rust battle. But for any milling that involves significant metal removal and non-CNC shapes that is my go-to machine. (Much more recently I acquired a Bridgeport, which is so much nicer than either the Shoptask or the Van Norman. But due to size and weight it is currently at a shared shop space 20 minutes from my home. So I still use the other two machines as well.)
After 20 years, I still haven't gotten a separate lathe. The shoptask works well enough as a lathe, and CNC makes threading nice. If I hadn't done the CNC conversion, I probably would have gotten a real lathe and retired the shoptask completely.
So that's my story. The Shoptask got me into home shop machining. It cost me $2000 in 1999. It remains the most expensive machine in my shop because I as I learned more I was able to get better deals on used machinery. The Clausing cost me $300, the Van Norman was $900, and the Bridgeport was a little under $2000 (the bridgeport was bought in 2019, so not the same dollars as the late 1990s/early 2000s). Only the Clausing and the Shoptask were able to come down the basement stairs.
Hope this info is helpful,
John
