The 2100, in my opinion, is far better for playing live. I had a PA80 and I did like some of the sounds. However, with the 2100, you will get mic input and a vocal harmonizer that works, plus fills, intros and endings that are many times better than the Korg. You'll find thousands of free styles for the PSR also.
If you can't tell the difference in the key feel, then I think it's a no-brainer. Most people prefer the Korg keys.
DonM