I know its heresy here to take a different opinion on the A-10 against the SU-25, and all Russian equipment is junk ;) but I might disagree with you. The Frog Foot has been enhanced as far as I know. There is the Su-25k and the Su-28. It can carry more payload than the Wart Hog I believe, and it goes 975KM/605mph on the deck. Each platform has its limitations.
http://www.airforce-technology.com/projects/su25/specs.html
But my thoughts were more to if we actually entered the conflict on Russia’s back door. I dont underestimate them.
The A-10 has also been enhanced. They are undergoing a major enhancement as we type. The result will be the A-10C.
Yes they are different aircraft, reflecting different design and employement philosophies. But they do have the same basic mission. Being faster is not necessarily better in the ground attack role. Maneuverability and loiter time both count for a lot when supporting ground troops. According to the FAS, the Su-25k is just the export version of the Su-25, while the Su-28 is another designation for the Su-25UT, the unarmed trainer variant. Perhaps you meant the Su-39 the most modern version, aka Su-25T The FAS shows the Su-39 having a payload of 6,000 kg, while the A-10's is shown as 7,200 kg, before modernization. The A-10 can be refueled in the air, while the Su-25/39 cannot.
The A-10 is more heavily armored as well, with better separation of vital components, like the engines for instance, but also including the flight control lines.
Then there is the matter of the quality of the pilots. Even the female A-10 drivers have big brass ones.