If I recall correctly, between the 1400 and the 1400i was the 1400i used 1/4" connectors instead of Speakons, and didn't have handles on the front. I sold off the 1200 about 10 years after i got it, but kept the 1400 as a spare amp as needed. Did have to send in the unit once for service for the ribbon cable issue. Painless repair, great service. Eventually one show out in the sun, the sound got all distorted and it quit. It sat around for a while, and finally traded it to a buddy of mine for some work he did. He likes fixing electronics, so it was a good project. Well, all that was wrong was a fuse inside, and the amp is still plugging along today.
The one thing I didn't like about the amps is that their air intake was on the front, and output was on the sides of the amp. This would result in some toasty warm amp racks, as the heat would build up inside. In an install situation, sometimes this could be desirable, if the rack is designed for that, but in my case it was a problem I had to deal with.
And of course, that was back in the day when Mackie was fun, and their manuals were some of the most entertaining to read ever.
http://www.mackie.com/pdf/m1400_m1400i_om.pdf Wonder if any company would have the balls to release a manual like that today. The lawyers would probably be all over it.
One of my later patents at Peavey was for an amp heat sink design that actually did something useful. 
