If you're after a one press solution for both handgun and rifle I'd suggest the 550 as well.
The Square deal is nice if you are willing to live with one press per caliber. Or at most change out the dies between calibers that share the same size primers or maybe primers and shell plate. But even that may prove to be a PITA. The Square Deals are intended for and best used as a one caliber per press sort of deal.
The big difference between the 550 and 650 is the use of auto indexing on the 650. You don't really want that for accuracy rifle reloading. With the 550 I just need to remove the case retention buttons around the shell plate and then I can place casings in at any of the four stations at will. So when used like this the press behaves as a sort of "super turret" style press.
Look at the caliber list for the 550 in terms of the caliber conversion kits. I doubt you'll find any calibers other than the very longest that require a special press anyway.
The Dillon 550 also uses totally standard dies of any brand you wish to buy. So no specialty stuff.
The downside? For loading handgun ammo there is none. It's fast. But not as fast as the much more expensive 650. The caliber conversion kits and die plates are also cheaper than the 5 position plates for the 650. Those that buy a 650 are also the sort that know they'll need enough ammo per hour that they will almost certainly buy case feeders and possibly bullet feeders. And that ups the package price.
My own press is a 550b. Now I do load enough that I could probably justify a 650. In a busy month of matches I shoot roughly 450 to 500 rounds. But that's made up of 3 and sometimes 4 calibers. To avoid having to swap the dies around all the time I try to load at least 2K of any one size before moving on.
I just haven't hit the trigger point yet. But given the fussing around needed to convert from small to large primers I could see myself adding a second press. And if I do it'll likely be a 650 with case feeder setup which will be dedicated to the small primer loading that I do the most. That way I can blast through the more common sizes like 9mm, .38Spl and .357 (loaded down for cowboy action, not full power) in a lot less time and get on with other things.
If was looking for my FIRST press I might also look at the Hornady AP. But do check the conversion kit sizes to be sure it'll handle your rifle plans. I suggest that because those with them tell me that it's not hard to disable the auto indexing if you wish.
Would I buy one? No. But that is based on my already owning the one Dillon. And I'd like to make sure that I can use all the accessories I've already got which are Dillon specific. That's why I'd buy blue if I do ever add a second progressive. But you're not locked in like I am.
IF you look at the price and it's more than you are planning on don't totally set aside the idea of a single stage for now. They are fairly cheap to buy and they have the advantage of using the shell holders that come with the dies. So no expensive conversion kits to use on a progressive when you'll be using it essentially as a single stage anyway. As I mentioned in the other thread once you learn and get your operations tuned up it's not difficult or rushed to zip out 150 rounds of handgun ammo per hour.
In other threads the idea of a single stage as a handy side job press on the reloading bench has come up a lot. I know I sure do find mine to be handy as hell and well worth the cost and space it takes up.
Having worked with all three styles, single, turret and progressive I found that for myself the turret is likely the one best option for a "one press for all needs and all time". But for that I tend to favor the idea of a Lyman or Redding turret. In particular the Redding has a fantastic primer handling setup. But since I run off more than enough handgun ammo to justify the progressive (and maybe even TWO progressives if I get lazy enough one day) I keep the single stage around for side jobs and rifle loading which I prefer to do on the single stage. In my case I opted for the Hornady LnL single because I liked the bayonet lock bushings that allows for rapid die changes.
Each of the presses by brand and model has a big play list of videos on You Tube. My suggestion is to watch a bunch of them to get a feel for how you see the folks running them and look at the tricks and hints if there are any. I think you'll get a pretty good feel from them about setting up and how would use them in your own loading.