ASI2600MC pro compared to ASI294MC pro. I am thinking of trading up.

It will depend on what type of telescope you are using the camera. The 2600mc  has smaller pixel  which will give you  better sampling in widefield images. To me, the main advantages of the 2600mc over the 294mc that make the replacement worth are:

• Much easier to calibrate. The 294mc tends to produce weird patterns mainly when the Peltier usage is high or doing long exposures  (longer than 5 min). This is more relevant when used dual band filters.
• The 2600mc does not have amp glow, so the need of darks may not be as critical
• You have much larger field of view.
• 16 bit vs 14 bit. This will give you more flexibility at higher gain  since dynamic range tends to drop

For the RASA, you will have to buy a different adapter since the filter drawer is too thick to get the spacing. Starizona sell those, but filters need to be installed in the back of the adapter. 
It will give you better sampling too.

Tim,
Go for it!  In addition to all of the advantages listed by Mike and Rodrigo, it ALSO has the newest technology: back illuminated chip design, where all the circuitry, etc., is on the BACK side of the chip, so you get better light gathering and resolution.
Also, the 2600MC Pro is now on sale at several vendors.  I've had mine for 3 years and LOVE it.  Some of the finest images on AstroBin have been done with the 2600MC Pro.

Ron Abbott