If you want to take my word for it, I've tested Class T fuses in comparison with Mega fuses and am currently also testing BS88 fuses since Class T is almost impossible to get.
The main thing a Class T (and BS88) fuse offers over Mega for the same AIC is that they are faster. This means that in addition to protecting the wiring (typical use of the fuse) they can also protect the silicon (like a BMS). You'll often see this symbol for this type of fuse:
A 'fast acting' Mega fuse, say a 200A rated one, will take 0.3 seconds to blow at 1000A. A similar rated Class T fuse will break in something like 0.02 seconds at 1000A - an order of magnitude faster.