Mike - I think thats the wrong way round, if you are talking about Interlace and Progressive.
In simple terms, Interlace displays half the lines on one scan of the screen, and the other half the next time round at 30fps, then you get the odd lines every 60th of a second and the even lines every other 60th of a second. (giving 30fps)
With Progressive, you get every line every time, so giving 60fps.
If you can go progressive, then do it, but to be honest, I can set mine to 720p or 1080i, and I cant tell the difference from the sofa.
Ive got a Pioneer Plasma, and a LCD upstairs. The contrast ratio on the Plasma is FAR superior to LCD. Which makes it far more useable in the daylight and for low light scenes.
LCD sometimes states a very high contrast ratio, but this will almost certanly be "dynamic" contrast ratio. The way an LCD produces this is it adjusts according to the scene. If its a very bright scene, the whole backlight is increased to produce a very bright image, if it is a dark scene the backlight is dimmed. Whilst this works very well, if you have a dark scene with bright spots - the backlight cant do both, so it comprimises, and you sometimes end up with a great dark scene, but with any light bits within that scene looking slightly washed out.
Then you have the "burn" effect to consider. Plasmas are inherrently more susceptible to burn than LCD.
If you have a static light image set on a darker background displayed for a long time on a plasma, you are risking burn. Whilst more modern Plasmas are a lot more resilient to this, they can still suffer it. More commonly, it is image retention, which means after a while of normal viewing the "burned" image dissappears.
LCD's are almost impossible to burn, (note "almost" - leave a static image on an LCD for a day or so and you may be in touble).
If you have kids that may leave CBB's on fo hours on end or any music channel that has one of those ridiculous static logos, it may be something to consider.
(look for a zoom function, so you can zoom a logo off the screen if that is a concern).
many programs are shot in fields though and so if you can have a telly that does both then that is better option. It's things that are shot on film or video shot on P mode which works best on Progressive scan. Sometimes you are prone to flicker if a video had been made to look like film.
Also consider the not so good black levels on a LCD tv.