I haven't watched the classic ones. There would already be a cultural gap between me, who grew up in the 90s, and the eras of the show, 60s and 70s. That is a bit of a gap on its own, and watching classic American television requires a bit of patience and an open mind for that reason. Watching a classic British show would make the gap that much wider. The show isn't as relatable to me as a young American.
I do plan to watch them eventually, but I'm waiting for the day when I'm willing to cross that cultural bridge into mid-late 20th century GB.
The 60s and 70s are a time of civil rights movements, war, protests, and new cultural trends in the US. I have no idea what is going on in Britain during this time (something with Ireland?). The show does make subtle statements about society and ethics (note the number of multi racial and same sex couples), so it would be difficult to pick up on that stuff in an older version of the show, when women's rights were still a topic. So, yes, the difference is significant.