Which tree is better cold tolerance? And grow fastest? Taller? Easier for maintenance?
W.Robusta is cold hardy to the low 20*s,Filifera is cold hardy to about 14* mabey lower.From what i've experienced Robustas grow faster than about any other palm.Both hold on to there old fronds that's dead, for a good amount of time.I would say Filiferas are less maintenance,because they grow slower.Good luck
Filifera has better cold tolerance, but if you live dont live in a dry climate it will easily rot. Its also slower growing and shorter.
Robusta is less cold tolerant (often begining to show leaf burn around 20F or not much lower without protection and death usually at 15F without protection), but is taller growing and faster. But in a zone 8a it will need some protection just about every winter and as it gets taller it will be harder to protect.
They both require maintenence in your zone especially since they may need occasional winter protection (especiall in wet climates).
They both prefer to be on the dry side but robusta can handle moisture pretty well (except when very cold). Robustas can be seen growing in wet climates like the southeast and florida, but you wont see many if any filiferas growing there.
The only filiferas I have seen in all of Florida is in front of a car dealership in Panama City on 23rd Street.