I personally believe the VC-10 is a better choice over the other two from an operating costs standpoint but you don't get the pax capacity you do get with the other two (can be less impacting with intense scheduling but if you do a fairly normal daily-routes schedule, the pax capacity will hurt revenue).
The 707 has the benefit of being in production at the moment but the 53 is just around the corner (couple months) with a smaller order backlog. You should get quotes on delivery dates for each and see which one you would get faster. See if there is a large difference (extra 1 yr wait for one over the other, I would decide purely on that - planes can always be replaced later but you can't get back lost time). For the VC-10, you are looking at a few years before first production, and that is a long time to wait with money tied up while competitors pop up and fill the routes you planned on flying and use up all the slots, not to mention the money would would have been making with a few planes in the air during that time.
If you really need a jet for your plans and you have the money today to start leasing, I would jump on whichever jet you can get the quickest.