Lightroom can perform many adjustments on images and I'd like to do >95% of my work in Lightroom, but I'm curious if I'd be getting better results by making the same changes in Photoshop. For example, will contrast, exposure, or saturation adjustments in Photoshop yield less noise on an image over Lightroom? How about burning and dodging?
If there is a minor difference, at what size print should I consider making these basic adjustments in Photoshop?
Lightroom (or Adobe Camera Raw, or whichever raw processor you are using) will have access to data that may or may not exist in the image after it is sent (as a bitmap/TIFF) to Photoshop. And it will be doing all of its math on the original image data, so there will be no rounding/quantization errors baked into the image before an adjustment is made, other than those introduced in the depths of the camera electronics (and over which you have no control once the shutter button is pressed - at least as long as you don't use the in-camera retouching features, if any).
Even when you know ahead of time that an image - say a commercial advertising image intended to be seen large and at high resolution - is going to require extensive work in Photoshop, it's good practice to do the "heavy lifting" in your raw processor (and use Smart Objects when you can, so you still have recourse to the raw processor). Raw processing may represent a very small percentage of the time taken on a polished image, but it will still be 90-95% of "the work".
Where Photoshop shines is in the subtleties. Used with a pressure-sensitive input device (a Wacom tablet or similar) in conjunction with tool flow and opacity settings, layer opacity settings, blend modes, layer and group masks, etc., Photoshop (or a near-equivalent bitmap editor) will allow you to make both finer-grained local changes to an image and much more radical sorts of changes (image compositing is an extreme, if common, example). You can work with more localized and more complex tonal changes, you can make colour adjustments that affect a narrower band of colours. You have access to many different methods of sharpening or softening parts of the image (well beyond what's included in the Filter menu), each of which is subtly different and may be optimally applied very specifically to the tones and textures that would benefit most from them. You have the opportunity to blend two or more "developments" of an image, each of which is locally optimal, but would be mutually exclusive in Lightroom (or other raw processor).
Those subtleties might not always seem so subtle, and they may easily represent 90% or more of the time spent with the image, but doing them well depends on starting with the best bitmap you can generate. It's that proverbial last 10% of the work that takes all of the time. Getting things as right as they can get in camera, then getting the best development you can get out of your raw processor is the first 90% of the job, even if it only takes 10% of the time, and everything that follows on depends on it. Photoshop can make a silk purse of of a sow's ear, but Lightroom/ACR is what makes sure that you at least have a sow's ear to work with.
