#1: AP 61/274 EDPH is an FPL53 triplet, the lens with the best color correction
#2: AP 60/360 PhotoLine is an FPL53/lanthan doublet. The color correction is very good but not as good as the above
#3: AP 70/420 ED is a doublet as well but the glass is not specified, that means it is the worst of the three
#1 is missing a rotator, the other two have one. If you want a threaded connection to the camera you probably want a rotator. The sell one for about $100 if you want to add it to #1.
They differ in focal length, obviously. How large an object fits the FOV depends on the sensor size. When you go for a longer focal length larger objects may not fit the FOV, if you go for shorter small objects do not show much detail. You have to make a decision what you want to do. In general a shorter focal length is easier to handle and less demanding on your mount.
#1 is know for a too short dovetail. If you want to balance it with the camera attached you have to buy a longer dovetail. f/4.5 on the one side is fast, collecting a lot of light, the downside is you have to focus very precisely. A slightly slower scope is a bit easier to focus.
#2 and #3 are missing a dovetail, so in any case you need to buy one. I don't know if they fit a tracker.
#1 is the only one with a decent mounting option for a guide scope.
A FPL53 triplet, flattener in the scope, rotator, a long dovetail and two rings, guide scope can be mounted on top, 3'' draw tube
The scope is only the second most important selection. Far more important is which mount you have/want to buy or if you want to use a tracker. If you have a feeling this is going to be a long time hobby you should start with a big solid mount. Over the years you will add telescopes because there is no one fit's all. On the other hand if you need something portable, e.g. to take on a hiking tour it is a different story.