I heard, so I thought that the WG65 and the SIM4 were identical except for the cocking lever. The SIM4 has the M16 style whereas the WG has the side handle. Otherwise, they have all the same parts, so it's a matter of which handle one prefers.
I have a Tippy 98 C, but thinking of getting one of the two above for scenario play. I guess it'll boil down to the cheapest one of the two I can find on ebay