I can only comment on the original Look pedals vs Time TBT because I've stuck with the Time since 1990 because I like them so much I've recently picked up some on ebay for pennies too (Titan Magnesium £180 new, 99p now on ebay!) although some have worn and clicky bearings.

The Time pedals are chunky but for me that's part of their charm. I started with Shimano PD-6401 Look pedals for a couple of years but although they're sleek, they're quite anonymous whereas the time are very distinctive, especially on an old steel framed bike with downtube shifters!

The main upside - you can move your foot how you like laterally and rotationally. The first time I rode them it felt very strange as if my foot was about to slide off but I got used to them quite quickly. There's also no way to to release accidentally. The Look pedal relies on the spring tension. The shape of the cleat provides leverage against the tension to unclip, but if you can pull the spring back, it will unclip (as happened to me a couple of times in signpost sprints with the Shimanos). With the Time pedals the cleats engage in the pedal and the red clip and the geometry won't allow accidental release, even if you could pull the spring away. The cleat needs to be rotated 20° to release, but as the spring isn't holding the cleat in place, but merely helping locate the cleat in the right place, release tension is lower.

The downsides? The plastic covers over the springs can come off and then they look naff. Also only a few shoes are compatible with the cleats so you need a plastic adapter for the look mounting which negates the much touted "bioperformance" closeness of sole to axle. However I've always used the adapter and can't say it feels any different to regular pedals. Finally there appear to be no spare parts, even on ebay, so you're facing a gamble on a set of pedals and hoping the parts you need are in those and ok. Oh and good luck working out how to get the spindles out, I still haven't worked it out!