Same engine, different size car. Assuming predominantly highway driving, and not looking for overly sporty handling, is there all that much to choose between the two? The 5-series seems to be the much more popular car...
I've debated (with myself) the I6 vs V8 argument, but keep coming down on the side of the 6-cylinder engine.
I really quite like the E38 too (just call me Transporter) but they seem to be a fairly rare beast over here.
Just thinking out loud at the moment.