Which is more powerful..

PS CS4 or Lr?

Do most people just stick to one?

For the purpose of retouching and resizing etc.

It depends on the level of editing you want to do and what you're comfortable with. Each program will do many of the same things. I use both, but LR gets the bulk of the workload because I like the cataloging features and I hate Bridge. But from there I do all of my exposure adjustments, sharpening, noise reduction, etc. Then if I need to do some more detailed touch up work I'll move to photoshop.

Power is subjective. But Photoshop allows you to do things that light room does not so if you were only to choose one it would probably be PS.

If you could only have one, it would have to be Photoshop.

+1 on Photoshop.
Unless $$ is the issue and minor/basic adjustment than LR. Otherwise Nothing can beat PS.

Its really not a fair comparison, while they do share some commonality they are two different beasts. They both share the same RAW engine and the only difference being the UI.

If by powerful you are referring to getting the most out of it, I would go with Photoshop. It can do alot of what LR can't as far as image editing. LR is more of a workflow tool that does some image editing. Everyone should catalog their files and this is where LR can shine though there are many catalog programs around. You can keyword and fill in alot of the IPTC fields via Bridge but that is all you are doing, populating the fields with no database behind it to support future searches. I don't mind Bridge as a file browser and it certainly has improved over the last couple of releases. Lightroom is where this really proves it worth. I can easily find a shot that I did a couple of years ago, assuming of course I did the key wording and such at the time I processed them.

If all a person is doing is some exposure and sharpening to their images then LR will work just fine but if one wants to go further and use the power of layers and the multitude of other pixel based editing then Photoshop is the tool to use. It is really a matter of personal choice and there is no right or wrong answer to this question.

You do hear a lot about Lightroom because it does so much of what photographers need that it is often all that is needed. This was, in fact, the intent of the Lightroom design -- to provide an integrated interface for photographers that combined tools for development, organizing/managing, and various types of output for our photography so that we could get a whole lot done in efficient ways. There are other Raw processors out there with great capabilities as well in various areas, but the only one that I know of that actually rivals the "all in one" design of Lightoom is Aperture.

But, there is one thing that users of Lightroom, Aperture, DPP and other Raw processors tend to have in common, and that is a capable "image editor", meaning an app like Photoshop, Elements, or, say, Gimp that has the featured for the more powerful and sophisticated ways of "manipulating" your images. There are, simply, times when a Raw processor is not enough, although the advanced capabilities of Lightroom and Aperture (and I'm hearing good things about the newer Capture 1 stuff) make more things possible with Raw processing than ever before.

It should also be noted that a current release of Photoshop CS has a matching Raw processor, Adobe Raw, with the same tools and capabilities as the Lightroom Raw processor so that if you have, say, CS5, you get everything that LR3 has for Raw processing. And, the latest update for the CS4 Camera Raw which is, I believe, 5.7, is not far behind.

So, for "one thing to do everything" Photoshop is still the champ, but for "one thing does most of everything in a well-integrated and efficient way", well, there is a reason why Lightroom has become a "tool of choice" for so many of us!

I love PS. but think you can work faster on Light room. If you take good exposures from the begning then you will spend less time in either program. You will spend time improving on your photos instead of correcting your exposures.