A few questions regarding filament

[curious aardvark]

lol round here people know who I am :-)

Ninjaflex is hard to print with. It's a very flexible and stretchy rubber like filament. A lot of extruders just can't cope with it.
Polyflex is stiffer and pla based rather than industrial rubber (polyurethane).

I find that for many purposes flexible pla is preferable to a flexible tpu/tpe.

I'm currently using a sunlu flexible filament - probably the stiffest flexible I've used to date.
I've just designed a print release hammer in it, on the grounds it's hard and stiff enough to make a hammer but the flexible side makes it damn near indestructible.

Going to put up a guide to flexible filaments in the near future :-)

As far as abs goes - unless you have a fully enclosed printer with a heated build area - it is an absolute bastard to get to print properly. Plus it's designed to shrink, so you end up having to resize everything before printing. The shrinking can cause cracks in the print and lack of bed adhesion, and yeah it does smell.

Essentially, pla,pet-g and most of the exotic and flexible filaments are much easier to print with.