Have heard great things about both and I like both from pictures. I am looking for continuous bloom, disease free, mounding shrub shape, 3 ft in size. . .your opinions?
In my zone 5 yard, Champlain would not be small enough to stay below 3 feet, but both of my LavaGluts stay compact and about 3 ft. high, fairly upright and mounded. In zone 8, Champlain is likely to be even larger. Both bloom freely for me throughout the season and are pretty disease free from blackspot where I am, but I give the edge to LavaGlut here too, since Champlain can blackspot and tends to canker a little more over the winter than I would have expected. LavaGlut is a darker color and more double, but the flowers are smaller. On the whole, LavaGlut sounds more like what you want, but in my case since Champlain was the rose that convinced me years ago that "roses aren't hard to grow" I have a sneaking fondness for it as well.
Champlain is tough as nails up here in Michigan's upper peninsula and it is a really nice red. I have Habitat for Humanity planted almost next to it. Habitat has black spot issues while Champlain does not. I planted Lavaglut one year and it was beautiful, but it did not survive my winter. Since hardiness where you are is not really an issue, either one would work.
I think somewhere Lavaglut's blooms from 1998 are still on the plant, still looking that dark red-black that they do so well. I agree it is more to the size you want (unless you grow it in south Florida on fortuniana rootstock where Ken Muncey had one that was eight foot tall with canes that could have been carved as table legs.)
My personal preference is for the bright red blooms of Champlain. I can overlook Lavaglut (although if you show roses you need Lavaglut for the Floribunda spray entry potential), but I love the red that is Champlain.