So I see Meng has just released a Jumbo and I know Taska released one does anyone know if either are fully accurate or are they like the old Tamiya kit that was horribly inaccurate

I don't have the Meng kit, so no thoughts on that one. However, I do have a couple of the Tasca jumbo's and they are excellent kits, IMO. You won't go wrong getting a Tasca kit.

Tasca / Asuka kits are NOT Tamiya or Italeri. (Though Tamiya's Firefly is a reboxed Asuka and way over priced) I finished mine a bit ago. (have 5 more of theirs finished or in the works) Excellent, and as far as I can tell accurate.

I think Tasca/Asuka are really the standard for how we look at Sherman kits. How the new guys will fit in remains to be seen.
Gary