I got a skater dolly for my wedding movies and I faced two big issues. It could not be used in outdoor events , as the surface is not even like the tiled floors.

Also, it can only take bottom or top depending on the support table.

So I started looking for a Camera Slider.

I found this two good and cheap,
Amazon.com: StudioFX 40" Pro DSLR Camera Slider Dolly Track Video Stabilizer: Camera & Photo (http://www.amazon.com/StudioFX-Camera-Slider-Dolly-Stabilizer/dp/B00BOGOT4M/ref=pd_cp_p_2)

and

Amazon.com: JRFOTO Camera Track Slider Camera Silder Video Slider 32" With Ball-Bearing Slide Mechanism By JRFOTO JS32: Camera & Photo (http://www.amazon.com/JRFOTO-Camera-Slider-Ball-Bearing-Mechanism/dp/B00BU91JD2/ref=pd_sim_sbs_p_4)

Which one do you recommend ?