I just transitioned to a Westco Gel battery from the 4th BMW factory battery. I looked at the BMW gel battery but was surprised to learn that they can NOT be charged with a conventional charger while the Westco gel battery can be. Also the Westco has more amp hrs of cranking than the BMW branded gel battery. These two points made this battery a no brainer for me.
If you use the Westco battery, be aware that you will need to drill out the holes in the terminal perches because they are too small for the stock bolts (on my RT). I over sized the negative terminal a little because was not exactly centered up high enough to get the battery connection on it.
I was having trouble with my voltage dropping below the 11.4 needed to initialize the ABS when starting the bike after sitting overnight. I kept fighting ABS faults and I knew it was time to get a new battery, but kept putting it off because they are buried so deep in the bike and it's a PITA to get to. This Westco gel battery is so strong that when I start the bike, the bike flips over four times in the parking spot and then the motor starts spinning. It's amazing the difference in cranking power.
I'm sold. Maintenance free and lots of juice means this is a good move by my book!