The is a thread dedicated to E53 v E70 check it out. From my understanding "first year problems" are a moot point because the brain can be reprogrammed and any mechanical part can be swapped out with a later model year. There is discussion about which transmission to not desire. There are numerous examples of members with both vintages.

I've been planning to get another E53 before switching to E70 mostly for cost and common part reasons as I will still most likely have two E53 still and numerous times I've borrowed a part from one car to fix the other (fuel pump, cam shaft sensor, DISA valve) or used one as an example of what to check for next when something breaks due to design flaw like the rear tail light I can fix the other preemptively.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)