At the risk of being overly prescriptive, after four years of grapple use on two CUTs, I'd suggest:
No CUT under 50hp or 3000lbs lift capacity in private use needs more than a 48 inch light duty grapple weighing at most 400lbs and ideally less.
Grapples were originally developed for skidsteer and front loader type applications which are very different than CUTs. Most grapples on the market are also more for commercial applications which as usual is a more intense environment than private use which explains why some grapples on the market weigh well over 1000lbs. Such grapples are a waste of money and actually perform less well on CUTs due to their weight. Would you mount a heavy duty Bush Hog on your 30-40hp CUT that is used only to mow your own pasture? Heavy duty or commercial duty is generally thought of as a good thing in marketing terms and we all are attracted to it but there are significant downsides to consider. Who has destroyed a light duty Bush Hog mowing their own pasture? Commercial duty is for commercial use. Don't be fooled into paying double or triple what you need to for a decent grapple.
There is also an easily understood misconception that grapples should be the same size as the standard bucket on a CUT. Wrong. There is almost nothing you cannot do with a simple 48 inch grapple that could be done with a larger heavier and more expensive grapple. The larger grapples actually can do less work in many circumstances as the net lift capacity of the loader is decreased. Wider grapples actually are more vulnerable to torquing forces and putting assymmetric (bad) loads on the FEL. Wider grapples distribute the digging force over a wider area and prevent you from digging as effectively at stumps for example.
Consider that big excavators which have ten or twenty times the lift capacity of our CUTs do not use large wide grapples but use heavy duty grapples that are only 36-48 inches wide when they are dealing with brush and stumps etc.
Wider grapples do make sense on a construction site where a skidsteer is using it to collect debris but that is typically not the use of grapples on CUTs.
So, I'll stop my rant but repeat that for 90+% of CUT users a light duty 48 inch grapple is a wonderful tool that is more than adequate for the jobs a CUT should be doing.