Many people will say that the only aftermarket plan that is worth it is the BMW Extended Warranty. Unfortunately, I guess you're not eligible for that (unless you were a late 2008 purchaser). [I have the BMW Extended Warranty and it started paying for itself this year.]

I don't know either of those plans but I would look at the plan that you can get through the AAA.

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2008 X5 4.8i | Wheels: Summer> style 336 20" RFT; Winter> style 214 Ferric Grey 20" RFT | Aero kit | ESS E-Flash tune | V1 | LCI Rear Tail Lights | Coding completed | Engine replaced at 90K