Try sequencing. Seriously - styles are just short sequences that get repeated every measure or phrase so naturally they are going to sound repetitive. Full-song sequences allow you to vary the backing throughout a song and give your music character. This is best accomplished with a computer although internal sequencers will work too. It's a craft unto itself to produce swinging sequences and they can free up your hands for playing a lot more than trying to control an arranger with your chording all the time.

The main thing I look for in any keyboard is quality of sounds, polyphony, and hard drive storage/playback capability of my midi files. If it happens to be an arranger then I will use the styles and/or create my own for occasional use but I will rely on my SMF's for most of my show. This allows me to keep building on a lifetime of unique sequencing work because the songs will remain with me even if I upgrade my keyboard later.

My dissapointment with Roland and especially Yamaha stems from their selective support - they purposely choke off any support for some keyboards while throwing their full support behind others. But that doesn't seem to be a problem for the Yamaha Tyros or PSR3000 which come standard with OPT voice editors that work within sequencing programs. I would think these keyboards would work quite well with sequencing programs like Cakewalk Sonar or Yamaha's SQ1.

I realize there are a lot of people who use styles only for backing and never sequence, but I think you are limiting yourself when that happens. There's a world of limitless performance possibilities open if you develop the skills to take advantage of the tools at hand.