We're moving to a new office, and doing some tenant improvements. Our compromise in the whole 'open office' debate is a few medium-sized rooms, with room for maybe 8-10 desks apiece, with individuals and teams sorted by distraction/noise level. They will have wonderful natural light from North-facing windows, but I'd like to replace the overhead lighting, which is currently old 4-ft T-8 fluorescent bulbs in pairs.

Is there an appreciable difference between LEDs and Fluorescent tubes?

Are dimmers appropriate in offices?

What about color temperature? Are warmer or cooler better?

I'm primarily interested in fostering a comfortable, collaborative, attractive, and productive workplace. I also understand that we will likely leave the overhead lights off most of the time...