I actually prefer DW6 strangely enough. I do understand the comment about the repetitive nature of DW but it's always going to be really repetitive and I felt the designers decided 'why try to be anything more' and work with that nature to create something interesting. It was very different from other DW games and had a massive overhaul. Let's face it, the most used combo in DW is going to be XXXY every time
Having said that I would say go for DW7 anyway, especially if you're looking for something that reminds you of previous generations of DW. I would also say that the best aspect of the latest game is the Story Mode, which follows a more progressive and naturally-flowing story, and sticks, far more, to the original story/historical events than other games have done. This made Story Mode fascinating.
I would actually say I'm a little disappointed with the Conquest Mode. Initially I though "fantastic, just like DW: Gundam 2"! But it's not really. Mission Mode in Gundam is a Hell of a lot more variable. Conquest is the same levels but with different characters that show up. I suppose I'd enjoy a lot more if I hadn't played Gundam 2