Hi LeighPing, the ones I posted a picture off have a right angled addition at the ends. Disadvantages would be,
1 - they will catch branches, undergrowth etc if you were close enough.
2 - if you did come off there is a definite additional "spike" to land on.... ouch
3 - you would have difficulty operating the brake levers if you were holding the extension, ....to name a few.
Yours are more like the ones shown but without the 90 extension on the end. They also look more comfortable on the hands if you were out for hours so I might look into those. I can't really see an advantage of the 90 degree ones, unless someone can convince me other wise.
How do you find those grips you have on a long day...