OK, a little more quick elaboration...mind you, this is with tweeters off, as I don't care for them:
The newer SVT 410hlf's, both Classic and Heritage, are still very low reaching, but the low end is a little less overwhelming than it used to be when SLM was making them, and the mids are a little more pronounced than they used to be as well. But while they do sound similar, the Heritage edges it out in overall richness. The highs are a little bit more twinkly, and it has a bit more overall presence everywhere else. This was in a store, and I didn't have the chance to sit there all day and go back and forth to compare them to be any more specific than that, but even in the store, it was noticeable. The speakers for the Classic are Chinese and the Heritage uses American speakers. Same design but there's a tonal quality difference IMHO.
The cabs themselves are the same other than cosmetics and possibly wood type (unsure of that one, though), and nothing jumped out at me that made one look bigger than the other. But they're both made of quality plywood and not OSB like the SLM-era cabs.
For an extra hundy, it's a no-brainer for me...Heritage. I doubt anyone at Ampeg would argue with you, either.