It all depends on if you will be using the raisen/nut dispenser and you would be making rye bread. A family friend has the SD255, but they rbought it for the ability to make rye bread. On the SD254 does beep to allow seeds/raisens to be added. But, myself I set it to make my bread for first thing in the morning. I have the SD255 and to be honest I haven't used the seed/raisen or rye bread for 10months.
But, if you will be making rye bread, then the SD255 is the only option as the SD254 does not allow for rye bread.
Thanks a lot for your response. I am keen on rye bread, so in that case it has to be the SD255. I would just hope that it comes down a bit in price again (I found the information that in the past it was down to as low as £80 here on amazon). Or maybe the price will drop further when the SD257 is our in the UK (already launched in Germany)..