As far as NVH, the 60*V6's have long been ahead of the Buick 3800, IMO, the 60's run much quieter and more smoothly; the new 3500 is ahead of any of the NA 3800's that GM ever put out in terms of power density (which, incidentally, is a meaningless benchmark anyway), and while the 60*V6's did suffer some reliability problems during the Series III years, those issues have since been fixed. The new LZ4/LZ9/LZE family of engines simply DO NOT have coolant flowing through the LIM, and thus it CANNOT leak out, it is not there.
The 3800 was (and still is) an excellent engine; and it's major claim to fame has always been the ease with which it is modified for power and how well it works in boosted applications. IMO, the new LZ4/LZ9 is a more than suitable replacement for the aging 3800.
06RANGER, I'd choose a Pontiac G6 before a current-generation Malibu any day of the week. The G6 is, IMO a much nicer car. Also check out the Impala, you can get phenomenal deals on lightly used Impalas. I bought my Monte Carlo with 9,400 miles on it for $10K off the sticker price.