I've used dual monitors for a very long time and I have found positives to exact matching, and complete mismatches. Monitors that are similar but not exact are irritating at best, due to the dot pitch being just slightly off.
Matching
Great for productivity. Documents, email, spreadsheets or any other kind of work where you need lots of windows open. I align these centered in front of me.
Complete Mismatch.
Great for home use, gaming, watching a movie, browsing, and videos. I use these by having the 32" directly in front of me and the 20" off to the right.
For work I used dual matching 22" @ 1680x1050.
For home I use a 32" HDTV @ 1080p and a 20" 4:3 1600x1200 Dell UltraSharp.