There is nothing worth keeping on either of those bikes. Any "upgrade" in frame will be totally lost with the spongey cranks and wheels.
Chas is right though, if you are really unsure about about fixed gears or track racing a dirt cheap bike may be a good idea. Another option is renting a bike at your track for a bit to see if you enjoy it, and want to put more money in. Here rentals are $10, so it would take you over a season to acrue the cost of buying on of the bottom barrel bikes.