Having owned a 3800 Buick Lesabre, a Grand Marquis, and a Toyota Avalon, I think I'm in a better position than most to comment on some of these posts.
First to address a few posts suggesting the Avalon is not in the same league as a 3800 or Panther I give you this link
The average vehicle has just an 11.8 percent chance of lasting 250,000 miles, but the latest iSeeCars.com study identified the 23 longest-lasting models...
www.iseecars.com
Funny, I don't see either the 3800 or Panther on the list LMAO
Second, I'd rate the 3800 higher than the 4.6 Ford because of the Ford's plastic intake manifold issues. I replaced mine twice in 80k. It's a common issue that is very well known and can't be overlooked when we are talking reliability.
Third, I'd rate the chassis of the Ford the best of the three. Body on frame is tougher than nails. I drove my GM very HARD. It also has a trunk that's huge compared to the others.
Last, I'd rate the ride of both the Lesabre and GM about equally, but I'd give the edge to the Panther's seats as the most comfy. Overall the Panther is the most comfy ride, the Buick second, the Avalon a distant third.
So far I have had zero problems with the Avalon, but I cannot compare it to the others yet until I hit the 100k mark. But I'd rank the Buick more reliable than the Panther. Not only did I have intake manifold issues with the Ford, but electrical gremlins also. The Ford also had some weird shifting issues until I started using Maxlife syn trans lube. I gave the GM to my best friend at about 120k, and it now has close to 180k on it, but the trans is slipping bad. I blame that on him because he flushed the trans twice when he got the car from me. You just don't do that to an older car. The Buick was fairly problem free until about 100k, at that time I sold it because of recurring cam sensor problems. However, after selling it I frequently saw the car around my neighborhood for several more years LOL