I have a Modwright with the XT upgrades and use a Hashimoto HM-7.
I haven't checked it against the MC side since I did the upgrades but before it seemed to expand the soundstage some. I think you mostly use a SUT to bypass an active gain stage.
The Lundahls in the Modwright are on the inexpensive side and Dan told me he chose them mainly for low gain since the PH9.0 already has tons of it.
Honestly I run the Hashimoto (1:15, PH9 at -6) mainly because I've always used them, back to my Darlington Labs days. I'm betting there are tons of happy non SUT Ph9.0XT users out there! I think if there's any difference it's small and nuanced would depend on the rest of your system and the cart.
I do like the extra gain sometimes as I do have some low, low MC carts. I don't run a pre and go straight into my amp (2A3 set).
If there is any improvement, again I think it would be small and it depends on you whether or not it's worth it.