Emu XL-7 & MP-7 User's Group

If you switch from the RM1x to the XL-7 you will lose:

random-access pattern selection, realtime groove quantize, realtime   
sequence control (velocity, duration, timing offsets), play effects (MIDI delay, 
harmonize, etc.), patterns > 32 bars long, the ability to switch patterns on 16th 
notes or bars, fractional tempos (130.1 - 130.9 BPM), mute groups, the larger   
LCD.

you will gain:

the ability to do grid edits while listening to other tracks (making it useable in  
performance),  patterns will switch at the end of the loop (generally better),  
more knobs, velocity and aftertouch sensitive pads, an extra set of MIDI ports,  
an extra LED display.

I'm not sure if theRM1x can playback sysex strings to other synths; it looks like  
the XL-7 cannot. The XL arpeggiators are much better than the nearly useless  
one on the Yamaha, but you already have them in your XL-1. If your XL-1 is  
not a Turbo then the XL-7 will also add the Turbo features.