No contest here - PSR1000 is the winner !
I also faced with similar dilemma not too long ago. I owned PSR1000 for 2 weeks. Also tried EM55 for an hour or so at the store. The store had both and YAMAHA wins hands down. The EM55 is like a lousy toy in comparison.
In my opinion, EM55 is a piece of TRASH compared to PSR1000.
The internal speaker is lousy in comparison with PSR1000.
Also, the button access is confusing compared to the YAMAHA.
Quality of sound - YAMAHA better !!