Advice on linear slides

I'm looking for opinions; thoughts on the pros and cons on linear
slides/ball bearing slides as compare to something like KMBW slides.
I'm thinking the KMBW type slides could have enough drag to keep the
table stabilized with minimal vibration compared to ball bearing
slides, maybe not, I see on Ebay most ball bearing slides has grease
serts. That good be good and bad, grease has a tendency to collect
trash. I don't know.
And, any thoughts on lead screws? Ballnut, Delrin?
I planned to build a very crude looking machine similar to the one
pictured on the group main page.
Any opinions, advice would be greatly appreciated.
Thanks
bill