Tastes change, tones change, business partners change, etc. It's happens in the music biz. EVH has through the years been endorsed by just about everybody. If you don't think Joe loves Strats and Teles, check out that picture of his guitar/amp collection. There are REDICULOUS amounts of Pre-CBS 50's-60's Strats, Teles, Fender Custom Shop, and Gigliottis. His music has simply taken a departure from the more American style blues ala SRV, Hendrix, Buddy Guy, Muddy Waters, (basically everyone but BB King) to the English style. Cream-era Clapton, Gary Moore, Truth era-Jeff Beck, Paul Kossoff, Jimmy Page, Peter Green, etc etc all Gibson guys more specifically Les Paul players.
To me, the Strats and Teles are more favorable to players who play through a cleaner sound. All 4 of Joe's amps are cranked up and geared for one thing. He seems to prefer to use amps of varied EQ, gain structure, tone, and headroom to get different levels of semi-clean to full blown gain. Guys like Eric Johnson, however, prefer to use 4 amps for seperate duties. The Strats really come handy for that bell-like clean through a Fender amp. My experience has been that it's much easier to achieve the overdrive tone that I prefer on a Gibson guitar, but the cleans are a bit lacking compared to a Fender. It's a sacrifice. As far as SG's go, I think it's just a matter of time until you see Joe with one in his touring linup. The are a bit awkward to play being so neck heavy, but then again so are the Firebirds. I'd love to see him bring a '61 Les Paul/SG Custom in Alpine White!
'67 and '74 Fender Twin Reverbs, '74 Marshall 1987 lead mkII, Metro Superlead 100. Pedals from TC Electronic, Ibanez, Dunlop, BK Butler, Electro-Harmonix, Fulltone, Maestro/Gibson, Loopmaster switching, VoodooLab, Boss. Gibson and Fender guitars, Dimarzio pickups.