I don't like third base or first base. First, it fits the stereotype, as counters supposedly prefer 3rd base and 1st base as second option, so I want to avoid that. Second, many places have the tables so close that both end seats are right up against the end seat from the neighboring table. This results in a sort of 'pinched in' effect, especially if someone is sitting in the seat next to you. It is hard to get in and out, and I am not even very big. Since I like to both enter and exit a game quickly and
quietly, drawing minimal attention, both corner seats are counter productive to that.
And finally, tracking two tables. If you sit in the middle seat or one of the two middle seats of a table with 6 seats, you
may have a nice easy view of neighboring tables on both sides, without doing some sort of aerobics.
You don't even have to turn your head that much, just roll your eyes a bit and depending on how many players are at the next table, you may have an easy clear view.
Number of players: We all know the advantages of heads up. But my preference is one other players. Two reasons. Double deck games, or even shoe games late in the shoe, I sometimes want to sit out a round or two to get to the shuffle. There is no sitting out a round if you are playing heads up. If you stop....the game stops. Second is related to the quick and quiet exit I mentioned earlier. I want to exit drawing as little attention as possible. When you exit a heads up game, mid game, you can't do it without drawing attention. The game STOPS.
The dealers attention is on you exiting and often the pit as well.