Bandicam dramatic fps drop
FRAPS gets its speed specifically because of the large file size.  When dealing with video you have two conflicting goals, low CPU usage vs low space usage.  To use less space, more compression must be applied.  To apply more compression, more CPU must be consumed.  

If CPU consumption gets too heavy, it impacts performance of games.  Thus FRAPS goes to the other side, rather than use compression, it saves nearly totally uncompressed.  This results in massive size files which hit the memory and hard disk more, but as most games tend to be more forgiving on these, it has less of an impact on frame rate as long as the memory and hard drive can keep up with the data rate coming out of FRAPS.

The fact you are trying to produce smaller files means you are running compression while the game is going.  This means more CPU consumption and thus lower frame rates.  If you want small files and good performance, use FRAPS and then compress down the files produced by FRAPS after recording.  Since they are basically uncompressed, there shouldn't be any measurable quality loss.