I switched to Afterburner from FRAPS for a while when I was playing BF3 also. Afterburner is a great free program. The only problem I had with it, was that it only records 1 sound source. You can either have it record your mic, and no in-game sound, or vice versa.
I found it frustrating that only half of the conversations in my videos were being recorded. Hence I went back to FRAPS so I can record both my mic AND in-game sounds. Performance wise, I found FRAPS to cause a lot of input lag when playing BF3 for me. Afterburner was not as bad, but there was still an element of input lag.
I get no such issues in Arma 2 / DayZ with FRAPS, hence why I use that. File size is not an issue for me since I added the extra hard drive. Plus I like to record in HD.
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