Yeah, Siege/ER definitely wins in the "gruff/ornery" department. SS86's noggin does look better in person than it did in pictures, though.
I'd say SS86 wins in the alt-mode department. Wheels and a cohesive back end go a long ways. The colour mismatch is nowhere near as bad as the maroons on ER, too (I find the red also pops more than ER's muted tones). I do expect Toyhax to come up with the missing yellow stripe and cover up the excess silver in front.
If I already had the various upgrade kits for ER Ironhide, I likely would have let SS86 pass by. But by the time you replace the feet and wheels, you pretty much spend voyager class money anyways. I'd say if you didn't have a previous Ironhide, get this one, but if you have a kitted out ER, then I wouldn't be so quick to swap it out.