Even though I don't like southwest, I have to admit that they have a safety record that is a great one.
I don't like how fast they taxi, nor how fast they fly their approaches, outside the marker.
I've been flying for a long, long , long time...domestic USA mostly, and I have NEVER landed or been to DENVER. I've been to LGA a zillion times but never been to Seattle.
But I do know enough that I would be very careful going to an airport that I had not been to many,many times...and then I would be careful because I would think I was getting complacent at the airports I go to frequently.
LGA, however is a straight forward airport , at least on runway 4. There are fundamentals of landing that can be masked at better airports...that is if you really don't land well, you will probably land less well at LGA. You will worry about going off the end into the water. Instead, you should concentrate on your spot (aim point) and your speed.
Taking over at 400' from another pilot is one thing, taking over from the autopilot at the same altitude is another....human selection of trim is a very individual one...some like a little nose heavy, some like a bit tail heavy...watch next time you switch control, and the other guy will almost always re trim.
so maybe the copilot had a nose down trim and liked the feel, and the captain didn't take the time to retrim to HER preference. And when she (SHE) relaxed, the nose dropped, instead of her personal preference to trim.
My best guess is that the decision by the captain was a spontaneous one and not well thought out. I think we would have heard by now from the NTSB something like...the copilot was out of control with speed excursions of over 30 knots (we sure did from asiana)