I approach a 10k merge and a deck merge very differently. I can think of some major differences between the two. Higher merge speeds at 10k, and no ground to limit options, and the ability to merge with larger amounts of vertical separation.
In a 10k duel you have plenty of room to dive and will usually merge at a faster speed than in a deck merge. Most of these 10k fights I've been in had both pilots going for the E fight right off the merge. I'd imagine that would be partly attributed to wanting to fly a safe merge for the tournament, but mostly to having tons of speed on the merge. I know if I merge at 430mph, I'm not going to open up with a flat turn.
I see, and do, a lot more angle fighting during deck merges. You merge closer to corner speed and have less space to play in. If I can gain a good amount of angles on the merge, or shortly after, the enemy has less speed and altitude to attempt and reverse the fight.
The majority of the 10k fights I've been in were decided by a long, descending, one circle fight from the top of our immelmanns down to the deck. Both pilots vying for the best turn rate. Whoever was more familiar with riding the best turn rate would be the victor. In a deck merge you don't usually have the altitude to stay in that turn long enough to gain enough angles from it. It will more likely result in a lufbery.
One of the fights from the last tourney had my opponent in a very steep dive before the merge intent on merging below me. I kept just low enough to keep him in the dive but high enough to not lose a ton of E trying to get under him. I was over 2k above him when we merged and had secured the E advantage before the fight had even begun. This never could have happened in a deck merge.
They're different.
