D&D 5E Mordenkainen's Tome of Foes or Monsters of the Multiverse if I don't care about new PC races?

[Stormonu]

Monsters of the Multiverse combines two book's worth of stat blocks from Volo's & Tome of Foes. You do lose a lot of lore, but that's only important if you want "deep lore" rather than making your own.

 

[delericho]

It's possibly worth noting that the lore that's missing from MotM is stuff that has largely been deprecated by WotC - that's one the reasons they've reissued the monsters in the new books. (That's a bit less true of "Tome of Foes" than "Volo's Guide", but only a bit less.) So if you have an interest in staying 'current', there's another reason to go for MotM.