Personal view here - Siemens is clunky, software maintenance is expensive.
Schneider software is really only suited to ST in FBs - hardware is expensive, software maintenance is expensive. Big plus is the ease of adding to FBS - a good feature.
RA is a bit clunky, hardware is expensive, software maintenance is expensive.
My preference is by far Omron - hardware prices are reasonable, buy the software and no update costs for about 7 years now - just update on the web, I am using the older series - still current and still new products coming out - uses CX-One - best ladder editor about for mine and soes have ST and FBs as well. I have not used the newer designs with auto I/O allocation at all or Sysmac Studio - the European guys seem to like it as it is more suited to ST but still has ladder that is OK and FBs. Full of structures and arrays and the like - same deal with the software.
I do use them all from time to time and have done a couple of jobs with the VERY expensive Schneider M580 dual redundant system - the price is ouch!
I would also say that for smaller jobs I would certainly use the AD stuff - the newer Click Ethernet processors finally have a decent amount of memory so online programming can be performed and they are inexpensive. The software is fine to use. Biggest problem I have in Australia is the absolutely lousy trading terms from the distributor here.
It may be good to have a look at Emerson as well - formally GE - they have some nice stuff but I have not looked at the software maintenance costs as I have not used one at this stage but did quote a couple of dual redundant jobs instead of quoting the very expensive Schneider system - no racks and even the processors were about 1/3rd of the price.
