Ultraflexx is a great product. I personally used both brands myself in the past, and I couldn't tell much of a difference in the quality, durability, or even print quality.
Ultraflexx = (13oz, 9x9 1000x1000 Denier, Flame Resistant NFPA 701 and CA Title 19)
Zeelon = (13oz, 9x9 1000 Denier, FR-NFPA701 test 1 and 2)
So, both brands are pretty comparable, and both are great banner materials. Zeelon is around .18 cents per sf, and ultraflexx is around .23 cents per sf.