I've tried H335, and like you say, it was a little faster velocity-wise, but the 3031 was noticeably more accurate. I can also use it in my .45-70, though it has a preference for H322. A case full of H335 can put a light show on in a .45-70!!
As a matter of fact, the 3031/Hornady 170 is a stand-out in my rifle, so if I'm forced to use another bullet, I may lean towards something like H335.
The Speer 170 is just about the only bullet I haven't tried, besides the Barnes 150 TSX. I have run the Speer 150s and 130s, and though the 130s were fast and accurate, I just wasn't too sure of their penetration potential, though I've since heard good reports of their performance on deer.
