The Elk web functions are built into the M1XEP ethernet expander. Both platforms have nice apps on the iPhone. For the Elk I strongly recommend
eKeypad. For the Omni I would look at the new
Snaplink. There are other iPhone apps available like H@me also.
One thing that the Elk with the XEP has that the Omni doesn't is mail support. But, that is one of those functions that you can always do in software.
While the Elk has it's web server built into the M1XEP, the "web" access is merely a web page containing a full Java applet that looks like a keypad. This means whatever accesses the page must support Java applets, not just standard HTML/javascript.
HAI's web-link just uses HTML and even changes to accommodate mobile devices, plus has a better layout than just a keypad. Web Link also handles emails, but the downside is it requires a Windows PC as a server. The upside to a Windows server is if you run a Windows Home Server and put web link on it, you will get easy to use free DDNS and SSL encryption for the Web Link web site.
If you run the Omni 5.7e touch screen it can handle email duties, but you will still need something else for remote access.
Honestly to complete an Omni system I really think you need a WHS, in fact HAI is coming out with a embedded WHS server of their own called the Music Gateway, that will run WL3 along with a music server for their distributed audio solution.
Elk has had a really big opportunity to make the M1XEP web interface much better, if it where a modern HTML/ajax interface with browser detection, it would be the best solution of the two, but IMO the Java applet is holding it back.
One last rant, I can buy a $50 router that has a full web interface built in with no additional hardware needed and yet neither Elk nor HAI can do the same with their panels? At least HAI has an ethernet port built in, but it is not much more than a high speed serial port currently. I can only hope the next gen products from these companies will be a little more advanced in network connectivity and management right out of the box.