Which pedals???

Between those to I would choose Ultegra pedals in a minute. Then again, I prefer metal to injected polymer.

Considering how many of each of those are out there being used daily I don't think you could go wrong either way.

i used look for many years and then switched to speedplay but I really liked both pedals to be honest, just remember both those pedals only have 1 sided entry unlike speedplay

Well, if you keep your shoes on the pedals then 2 sided entry is really a moot point, but I do like the Shimano. Hell, the R540's are only 45 bucks at pbk.

Have ultegra's on both my bikes, woudn't switch them for anything.

Ultegra's. I love my shimano pedals.

The ones you practice with
Seriously, they're both adjustable.

Love my Ultegra pedals, but I'm tempted next year to test some Speedplay since they are double-entry.  It would definitely save some frustration when I don't clip in the first time during an event (I'm not a flying mounter.....)