Fit will vary in a HUGE way between grips. You will see the extreme undersized panels which show over 1/8" of frame all around and just look terrible up to the custom fit handmade grips and everything in between. Besides the fit of the grips to the frame, there are also issues of difference with thickness and shaping. A properly radiused grip panel will fill your hand and be pleasant to hold. The low side of grips can be a basic block with slightly rounded corners that will leave your hand bruised and sore. Again, there is everything in between available also. Textures - Some people prefer smooth, some light texture, some heavy texture, some would love to glue boulders on there and that still wouldn't be rough enough for them. Finding the right combination of all these factors for YOU is the challenge. When you find the right combination of elements for YOU, not only will your shooting sessions be comfortable, you may be surprised at how much your accuracy with the given weapon will improve too.
Many brands and makers out there, just take the time to get the answers to the questions on the factors that are important for YOU.