Thank you all for the advice and replies! I’m not much of a modded/tuner when it comes to the M cars I’ve owned previously, and after test driving a 2016 I don’t think I need an ounce more power lol. I NEVER buy modded cars for this reason, either.
The truth is I tend to buy the M cars because they have better interiors, better brakes and subtle but worthwhile body enhancements, and they tend to hold their values better than non-M cars. The power is just icing on the cake for me (I live in NY and sit in traffic constantly with my big stupid V10...)
Anyways, as a follow up.... it seems like the E70 is literally half the price of the F85 chassis. Is the F85 really twice as good, or should I keep my eye on a really nice E70 instead?
I’m more concerned with the power (same) and the handling (same) of the X5M. I believe the two to be very similar in that regard.
Thanks again to all, making me feel better about the transition.
E70 may be half the price mainly because a 2014 model is missing, making a bit of a price gulf. I own the E70 S63 as I mentioned before (stock) and I've put tons of miles on it with no engine issues. I change oil at half intervals 7,500 miles. To me, oil covers every part of the engine and runs through some hot turbos. Seems to me that it would shorten life given the application the oil is used for.
Main bearings being an interesting topic, I believe I can hear the mains on this engine making a bit of noise, but that typically isn't as fatal as a rod bearing and can pound away forever. I've noticed over the years that main bearings tend to be more of an issue on higher torque engines.
You can pull away easily from most traffic with under 2k RPM, 2500 is good to put you about 6-10 car lengths in front of grandpa Hal. Tons of twist. Exhaust sound will have you be the laughing stock of the pony car crowd no matter what you do to it. Who cares, it's a better vehicle than a Camaro.
Driving the F85 the engine sound coming over the speakers is fake, almost irritating... the transmission is very busy shuffling through the gears at low speed. It's noticeably faster in most RPM ranges, peak acceleration is more a function of the 8 speed gearbox, as once up over 100mph the acceleration feels about the same.
Interior-wise the ambience in the F85 is worth the price premium. The E70 interior is based in 2007 (with echoes of 2005 E60 and even earlier design language). If E70 is your choice, find one with the comfort seats and 2011+ (LCI) it'll have similar features as the newer F85. Comfort is about the same. The E70 depreciation-wise is near enough the bottom, at least here in Canada, with 2013 values closing in on 2010 values. The F85 is still on it's way to the bottom.
I can't seem to get a proper alignment on it, the inner rear tires wear out pretty heavy, the front gets feathered edges. You're into trailing arms bushings to get this corrected, but it'll eat your tires alive.
The E70 has a lot of charge cooling issues and body electronics stuff to correct. Airbag recall, driveshaft recall, door handles stop working, backup and overhead cameras and modules, iDrive module, charge cooling pumps on their third go-round, air suspension leaks and compressors, $3,000 brake jobs, $1200-$2,000 tires every 20k miles, crankcase vent tubes harden/crack/leak over the top of the engine causing vacuum leaks, plugs and coils, fuel injectors need to be the latest index or they'll go bad, interior squeaks and rattles, and I've replaced a high pressure fuel pump. All under warranty, which is about to expire! Not sure about F85 in this regard. Both will see about 12-16mpg, the F85 being slightly better as it revs a lot lower down the highway and has the variable lift/better aero. In the winter I've been down under 6mpg around town.