I vote for a well cared-for 2003 4.6iS...one can add all the power options they wish, on a 4.4i but if it ain't forced induction tuning...it ain't the same experience, imo. There are a dime-a-dozen E53's on the roads but very few 4.6iS' as they were interim and limited production. There's a higher threshold for tuning than with other E53's so if you go that route, you'll have a monster on your hands. The next best thing, is the 4.8iS, obviously.

It will be a tough hunt for a well maintained 4.6iS...Besides the general things to look for, cv boots etc...the most common problem to look into is the torque converter (TC) and trany. The 4.6iS has a higher stall TC and is common to fail with higher mileage. If the trany has been repaired, inquire if they replaced the sensor in the trany and if they replaced the TC.

I've had plenty of experience with both models you're seeking so feel free to reach out with any questions...Happy hunting

*Edit: my comment may not make complete sense in it's entirety, as it was a partial response to a poster within this thread that deleted their entire post