Sounds like Rhino Dave has a better grip on that setup. I would guess there is probably a $25-30 difference in price between the two derailleurs? I have a 34 tooth low cog (8spd cassette) on my touring bike since 2006 and I haven't ever wished I didn't have it
. I remember a long hill near Coaticook Quebec I climbed two years ago I would have loved to have a 36t!