Can you compare this two linear motion parts

[bunalmis]

Can you compare this two mechanism.

What are the advantages and disadvantages?

[CJL5585]

Bunalmis:

If I were purchasing a unit, I would purchase the unit in the first photo. (with motor)

Both units require extensive machining and accuracy to fabricate. My personal preference is linear bearings because they are self cleaning and very accurate. I do not see any disadvantages in Photo 1 except that it will be more expensive to fabricate. I also believe that it would require less maintenance.

Photo #2 with roller bearings are not self-cleaning and can become covered with particles from the material being machined. Also, one would have to deal with alignment problems with all the roller bearings. Additionally, there is a possible problem with repeatability and accuracy.

Jerry