Don't take this as a criticism. You've detailed quite a specific set of circumstances. This is detailing the standard nose-to-nose vertical merge tactic which in the vert is still a turn-contest, but climb rate helps out here espc if you go into a 2nd nose-up nose-to-nose merge (2nd immelman). This scenario assumes co-E, cold-HO even-steven's merge - this rarely happens outside the DA, but is still worth mentioning with the appropriate caveats. Not all of these types of engagements will continue into a 2nd immel merge either, often the 2nd vertical turn is an oblique climbing turn as they dont have the E to fully complete another immelman with speed to spare, or one party just extends away knowing they cant compete vertically anymore and are prepared to be on the defensive.
All the same, its worth mentioning whats going on in frame 1. The dive towards each other is not necessarily about picking up as much speed as possible, but often is more about trying to get under your opponent on the merge and start a lead-turn in the vertical which should enable a snapshot opportunity shortly before the 2nd merge as the lead-turner will have his "nose around" earlier than the other typically. The person at the bottom on the merge who has pointed his crate upwards prior to the actual passing will typically gain enough angle for the aforementioned snapshot shortly before 2nd merge (cause they have already started his turn before their opponent). Your opponent may recognise what your up to, and dive down to attempt to cut off any vertical seperation which can be used to lead-turn with. Often, i chop the throttle on my dive to avoid getting too much smash to help keep me closer to corner velocity, and thus increasing my chances of getting my nose around 1st. Its a tough call whether to blow your E for the angle advantage pulling high-Gs, or whether to allow your opponent the bottom (and thus the angles) and let them execute a high-G reversal while you execute a nice fast n lazy low-G climbing extension then reverse with the E advantage. You have to make the call before the first merge and live (or die) with it. Often its easy to tell if they are going to go for the vert lead turn (eg they very aggressive in taking the low position first), other times it can be a bluff...
Check out the netaces write up on lead turns:
http://www.netaces.org/genmerges/leadturn.html#title
