I absolutely agree. To quote a forum member from a few years back, "The 8500 AT reminds me of some NYC lawyers with the double breasted pin striped suit, the cufflinks, the contrasting collar and shirt, the tie clip, the collar stays - just too much going on for my tastes even if the quality is high."
The 2500 series Railmaster and AT are classic designs that are comfortable and have an uncluttered look. While the 2500 AT is one of my favorite watch designs of all time from any manufacturer, I wouldn't even wear the 8500 AT.
IMO, Aqua Terra 2500 > Explorer I > Aqua Terra 8500
Unless your wrist is particularly large, I'd go 39.2mm. It wears large in diameter, due to the large face. It is nice and thin, though, so it lays flat against the wrist compared to my Sub Date, and my Sub is slightly thinner than an AT 8500.
Honestly, with a 6.5" wrist, I'd go with the 36.2mm AT 2500. It still wears larger than the 36mm Rolex watches.
Here's my black AT 2500 on Perlon: