Is the SLX XT 151 and the SLX MGL 71 the same size body frame? Or is the SLX MGL 71 smaller. I know the spool size is smaller on the 71 vs the 151. I'm looking to find out which one would be more comfortable to grip while fishing or are they the same.

Frame and side plates are shared between both models. Handle and knobs are different/smaller on the MGL.

^THIS^, and they are VERY comfortable in hand.

I don't have an Slx XT, but I have a couple of the SLX MGLs and really like them. They cast awesome, are very smooth, and are small and palm well.

I bought an SLX XT in March and used it this season paired with a St Croix Bass Mojo spinnerbait rod.  I love the big handles it has.  I fish a fair amount in the rain and the big sticky rubber handles really help to get a hookset when its wet out.

The slx mgl/xt profile is my favorite to palm hands down.