The 235-grain Speer .375's are Hot-Cors. The 270-grain boattail spitzers are swaged. There's been a difference between the Hot-Cor and Speer BTSP bullets for years, even though a lot of hunters assume they're the same.
The Hot-Cors use a fairly hard lead alloy--which is pretty easily done since the core's "inserted" as molten lead. (This does NOT mean, however, that Hot-Cors are "bonded," as some people assume and even Speer's past advertising sometimes implied. Molten lead doesn't bond to a cold jacket.)
The BTSP's, however, are made like most other cup-and-cores, by swaging the jacket around a cold lead core. To make them easier to swage, Speer uses a relatively soft lead alloy. As a result they don't usually penetrate like Hot-Cors.
