The Only Advantages I see Sandslash have over Excadrill is Neutrally to Fighting and Ground Moves, especially Mach punch and Earthquake, so you don't have to worry about Conkedurr ruining your fun and you don't have to carry a balloon.
You're still walled by physical walls like Skarmory and Gliscor and Hippodwon etc...
You're Vulnerable to Toxic, decreasing your Sandslash's Life span
Lower Speed at base 60 I think (I'm just guessing) means some Scarf users out speed you and KO you, I think Scarf Latios can come in on a Predicted EQ and proceed to KO you on your weak Sp-def side
I fink Sandslash has a High Def stat, something like base 110 (I'm guessing again) so it should be able to take those neutral Physical attacks.
I can't think of any other pros and cons, between Sandslash and Excadrill.
I wonder if Sandslash will be banned from UU, as the only reliable counter I can think of it Azumaril Mamoswine and Weavile, Do Scarf 100s outspeed Sandslash in the sand?