If you can keep it under 10’ (including two 90 degree bends) flex should be fine.
If it is longer, if there are many bends or If it is in a concealed space (like within a floor/ceiling cavity) I would recommend smooth metal duct.
Flexible duct is meant to be used in places where it can be seen/maintained, unless it is only moving air like for a bath fan or for an HVAC duct. If you can see it from the basement it should be OK.
In any case a smooth metal duct impedes air flow the least.
They say the 
can blow 10’ plus two 90 degree bends.
I calculate that to be a 20’ effective length.
You can calculate your effective length by measuring all straight pieces of smooth duct and adding equivalent lengths for each bend depending on how tight the radius of the bend is based on this post.
If the total is less than 20’ then you should be fine. If it is longer then consider adding a booster or better yet just spring for the filter.