Roland VA series vs Yamaha PSR series ?

hi everyone,
can somebody please tell me the pros and cons between the roland va series and the yamaha prs series for songwriting purposes ?
also what is the main differences between the roland va-3, va-5, va-7 ?
thank-you

I will answer the second part of the question first (it's easier).
VA5 and VA7 share the same sound engine, the same samples (48MB), same styles etc. The differences are 4:
1. Aftertouch available only on 7
2. Variphrase section & mic in on 7
3. ZIP drive on 7
4. Ribbon controller on 7

VA3 has many differences with smaller sample memory, less styles etc. I wouldn't recomment it.

Now, PSRs are more oriented to live use in my opinion. I wouldn't reccoment nothing below 740 or course. They have more buttons (while on roland you do many things through the touch screen), pads etc which make your life easier on the live. I could say that roland have better sound quality but that's not objective. PSRs also offer simple endings and intros which is one of the biggest ommissions on VAs in my opinion. That's a big discussion and I don't cover everything, but whichever you choose you won't be dissappointed... (no VA3, no less than PSR 740 or 2000)

thanks for the clear explanation.
i have one more question.... how are the styles in va5 or va7 compare to the... say prs 2000 ? i would really appreciate this answer. thanks
ps. i'm into r&b, hiphop, pop, electronica

There are only a few of the styles that you mention in either brand. These boards are more geared to a "Mom & Pop" croud than a bunch of kids. You can create your own styles, though .... and Hip Hop till you drop!