I have the Penn State hay probe. The barrel is longer with a smaller diameter than the Master Forge Probe which has a shorter barrel of wider diameter. Just my opinion but I suspect that the Master Forge Probe would be the better choice of the two. The two probes may produce about the same amount of cut hay per sample. The Penn State probe being longer creates more resistance (an heat) as you push the probe into the bale. You have to go deeper into a bale of hay with the long skinny probe to get the same amount of hay that the short fat probe will cut/collect. Also the cutting head on the Penn State probe will have to spin/cut longer for the same amount of hay which means the cutting head will have a faster rate of blade dulling.
This is just my "guess" at the benefits of one over the other. By the way, I suggest you use a good quality electric drill over a cordless drill.
Bonnie Snodgrass 07-2016
ECIR Group Primary Response
White Cloud, Michigan, USA