nods in agreement
Becoming a catchphrase now.
For the user, the core functionality should be pretty similar. With the exception of the image hover thingy which I dislike and won't put in as part of the core just because. Actually, for the store owner that is up and running I don't think there will be too much difference. Both will run quite transparently. Install for the user is easier at the moment with Image Scaler but I am sure that this will change when IH4 is released.
Also for the user, I think that the additional image uploader is simpler to understand. Meanwhile, the inclusion of 'variants' which allow the replacement of any scaled image with a alternate image is probably a bit more powerful than the way IH works. There are also a few unexpected strengths in that system. For instance the ability to have product listing images that are different sizes for different products.
For the developer and the person who is interested in the code I'd say that the code and methods of Image Scaler are a bit simpler, but I would wouldn't I? The aim all the way through is to strip down to the bare necessities and I am really going to try and keep it that way. Most of the 10 or so files in the present version actually have to do with the 'clean-up' which although not a core function seemed like a really good idea. As I have said before I don't think that the core module should do anything other than scaling images and serving scaled images.
Extra Thoughts:
Having said that about the image hover thingy I have a client who loves it so am in the process of making a version of that anyway. The most recent version of image scaler contains a few bits and pieces that are aimed in making further image manipulation modules easier. The main thing really is that the image paths that are used on a specific page are stored into an array so that they can be used later on. For in the case of the horrible image hover thingy that means that the larger version of the images can be preloaded in the footer. This might also be helpful for lots of other jQuery niceness like zoom features, lightboxes, anything that needs the images used but not necessarily visible on the first load of the page.