Cool test, guys. My reading of this is that you used the Sandia Crest MegaLink repeater for all portions of this test. A repeater at high elevation makes a big difference. Yaesu makes good equipment, the FT-2800 has a good reputation. I have never looked closely at the VX-170, but the eHam.net reviews look good.
The standard "rubber duck" type antenna used on VHF handie-talkies are relatively poor performers. Gain figures look more like -3 dB to -6 dB. However, they are short, flexible, and do the job.
If you want to see your HT come alive, use a "Hot Rod". This was a collapsible end-fed half-wave made by AEA. I don't think AEA makes the Hot Rod anymore, but I have one made by MFJ and two by Larsen. Some years ago I climbed Handies Peak (a 14,000 ft peak near Lake City, CO) and talked on 2M FM direct with a ham on Sandia Crest. I had a 5W hand-held with a Hot Rod, and he had a similar hand-held with some kind of portable beam. The distance was approximately 300 miles!
MFJ now calls this the MFJ-1714 LongRanger Telescopic Endfed Halfwave 2 Meter HT Antenna
MFJ Enterprises
73,
Andy
N5GIC