Currently, I use a Pana 45-200 for bird and wildlife photography. Last week, on a excursion, I found that I desired a little more reach than 200mm. I'm looking at both the Pana 100-300 and the Oly 70-300. I currently have the Pana 20mm, Oly 14-42mm, the Pana 45-200, and an adapted Canon 50mm FD, all on an EPL-1 body. Any thoughts, specifically on the 100-300 vs. the 70-300 as it pertains to build quality, optical quality, and real-world usage? Thanks!