I recently acquired an Epson 4990 which is bundled with Silverfast SE. I've been using Vuescan with my former scanner for some years and I like it o.k. for the mostly black and white photography I do. But all other things being equal I'm inclined to switch to Silverfast (and maybe upgrade to Ai) because I like the ability to see the effect of adjustments on the image as you're making them, which you can't do with Vuescan. However, I don't know anything about the relative merits of the two from a scan quality or any other standpoint.
If anyone here has used both Silverfast and Vuescan I'd be interested in hearing your thoughts about their relative merits. Also any thoughts about the wisdom of upgrading Silverfast SE to Ai. I don't mind spending the money but not if all I get is a program with a bunch of extra options and features that are only useful to pros or other people who scan in large volumes. I've read what Vuescan says about the advantages of Ai but I don't understand half of it and don't know how relevant the other half is to someone like me who scans only large format in a very small volume. Thanks.