4.6is vs 4.8is Common Issues - which is worst?

[efifty]

I'm fairly new here, but been a lurker for awhile. I'm finally searching seriously for an X5 and conflicted between a 4.6is/4.8is.

no doubt, both will require big ticket items after purchase. But which is worse? The coolant pipe/valve seals/levers of the 4.8is or the timing chain guides of the 4.6is?

It sounds inevitable for the tc guides on the 4.6is, and coolant pipe on 4.8s... but valve seals, is that certain?

I looked at the diy thread of the tcg, and that does not look fun. While I am a diy'er, that looks pretty tedious. On the other hand, valve seal replacement is big $ from what im reading. Any inputs on what actual costs might be from an indy? I dare not ask my indy because he'll just talk me out of either or instill fear.

I was initially looking for lower mileage cars, but now im thinking of pivoting to higher mileage with big ticket items already done. I did find an 4.8is with valve seals already replaced, same goes for a 4.6is with tcg already done. however they are 130k plus cars.