I did the swap from Tremec to an Art Carr AOD last fall, and I love it. I'm not bashing 5-speeds because I still like to drive them. But a few factors came into play for me to make the swap. One, I was adding a blower and didn't want to miss a shift under boost, and I was getting tired of the clutch in traffic when I drove in town. Plus I never had an auto in any of my stangs and wanted something different.
My AOD has the auto/manual valve body,and can be ran in full auto or manual. And I run it as a manual 99% of the time. Also I have a sorta big converter (3400) and it does kill some mpg, but drive-ability doesn't suffer. I average 14-15mpg's around town. The AOD is eating up more power to run the the 5-speed, but I don't mind. And even though my car was set-up for boost(8.5:1) and 5-speed(3.55) gears it still ran some 12.80's on motor at 3450 race weight and Nitto's. Now will some more gear & compression, I think some mid 12's would of been no problem. IMO the auto in manual mode is as fun to drive as the stick, but that is me. Pretty much when you come to a stop you have got down shift and so on...but, no clutch. I'm not bashing a 5-speed, just giving my experiences with my AOD, compared to when I had a Tremec. swap
But if you don't plan on a power adder, then the 5 speed swap should be considered. It would be cheaper than a good AOD set-up. I did the AOD to 5-speed swap on my brother-in-laws 90LX fews years ago and found a wrecked LX for $700 and got all parts needed for the swap plus extra.