Extralite was the original plastering trowel by marshalltown in UK. Permashape was introduced later.
I Now use a marshalltown duraflex a straight trowel with a tiny bit of flex with a wooden handle.
The latest one is a permashape duraflex with a standard marshalltown handle.
It is down to personal choice.
Although I’ve had a few over the years and still have kicking around, I don’t like permashapes as they have that curved blade and a 13” (for example), ends up only having about 11” contact with the surface. I get laying on doesn’t leave lines at the toe & heel with perma but 30years ago all MT were straight…never had a problem.