If you see who are the next to act in the queue (like Pathfinder, for ex), it makes it tactically very interesting to interleave fighters of both camp. Not only you have to manage the initiative to get your fighters in a comfortable order, but you also have to take enemies into account when you plan your tactical actions.
When the whole party acts at the same time, it's usually too easy and unrealistic. A whole part of tactical planning goes away, and it unbalances the game by giving a lot of advantage to the starting party, so there's a need for artificial subterfuges to counter-balance it, like here (e.g. one party being able to position while they're under attack, and the other team just watching them while they had the initiative).
I'm sure it'll be fun either way; we'll just have to see how well those elements counter-balance one another.
