This might be too specialized a question, I guess we'll see.
I haven't driven the new Mustang with the V6. I have driven it with the other two engines, and I was impressed by the level of refinement and how well the new car steers and handles--far better than any previous Mustang. I've been saying that if someone thinks they might like a Mustang, they'll probably like it a lot.
We don't have enough data to provide reliability stats for these yet. Probably with the May update.