You can cut a 2x6 on a 45 with a 10" slider. If you want to compound cut, get a dual bevel. A 10" will just get through a 4x4.
Ron

Thank you,Ron.
I will need a consensus on this as another man posts that only a 12" will perform well..
The 4 by 4s will be cut at a simple 45 degree angle.
What is the dual bevel ??
TIA

Dual bevel tilts both to the left and right. I have all three of your listed saws. All Makita. Just bought the 12" from Amazon last year for $396.00, delivered to the house. Since I do house remodeling it's also tax deductible. Sort of a win-win situation.
I bought the 10" slider about 20 years ago initially for a deck. It can cut 2x6 on a 45 degree setting and could cut 4x4's just barely. The 12" stays in the shop. Very rarely does it have a use in the field, so far.
If you want to spend the money on a 12", go ahead. You might find it needed on another project in the future.
Keep an eye out at Amazon. You can get some great buys if you catch them. To check online tool prices, go to www.toolseeker.com. It will list various manufacturers and you can compare features as well as comparison shop for price.
Ron

Thank you, Ron.
My source is Harbor Freight
OK, I think, for occasional light duty use.

You might want to post over on the Woodnet forum about Harbor Freight power tools. Someone might have experience with the saw you're contemplating. I don't have any experience with the Chicago/Central machinery line.
Ron