Hi there.
Neither keyboard is better than the other as they all have their good points, at the end of the day it's a case of listening to them all and deciding on what you prefer and hear. The Ketron and Tyros 2 are easy to operate, I've not seen the Korg but many users on here seem to love it. My neighbour has the G70 but he didn't like it because the sounds had too much reverb on them, this has been corrected I think as someone stated in a recent post with a new operating system update.
For me I own the SD1, Tyros 2 and an older Roland G1000 (not forgetting a Triton pro). The SD1 and Tyros 2 are totally different. The SD1 seems to have more bass end to it but I prefer the styles in the Tyros 2 as they are more suited for the music I have to play. The SD1 has great sounds and a built in hard drive, the Tyros 2 has super articulation sounds which when you've got used to them and played live sound fantastic.
I notice that you have posted elsewhere stating you do not actually play the keyboard but want to play midi and karaoke files. Depending how much budget you have I would consider something like the Midjay. This doesn't have keys though as its more of a rack unit so you would not have the comfort of hiding behind a keyboard as I know some singers like to have. It is a fantastic product though.
It can be a bit daunting standing at the front of a stage possibly on your own, where as behind a keyboard (regardless if you are playing or not) offers some comfort I guess and more security - think peeps on here will know what I mean.
If you are seriously wanting to get a top end arranger keyboard please consider having lessons so you can learn to play and thus reap the awards of playing your own songs, it has to be far better than playing to pre recorded tracks?
Another alternative would be to get a cheap 2nd hand master keyboard and maybe something like a Roland sound canvas (giving my age away here lmao) or another rack mounted box of tricks/styles and just midi it to the master.
You've loads of options so best wishes with whatever you choose, good luck
By the way I am back for good. After quite a few e-mails and kind words from the likes of Scott Yee on Skype (cheers bud) I've been persuaded to stay as I've been on SZ for about 6 years on and off, so it's a lot to give up just for the sake of some silly misunderstandings/postings.

[This message has been edited by Craig_UK (edited 02-01-2006).]