I only have 16"s and 24"s...none of my needles are curved. The needle part is totally straight and the cord is sooo flexible.
As far as size goes....it really depends on what you knit the most. I have a lot of 16"s because I knit a lot of socks and kids' items....I've just started accumulating more 24"s which are great for bigger things like sweaters. I'm not sure about what's best for blankets because I don't knit them. :D
Knitter's Geek Code
KCR+ Exp+ SPM+ Steel+ Bam+ Addi++ Pl-- Wool++ Cot Lux+ Stash Scale+ Fin !Ent Int FI> Tex Lace Felt Flat Circ+ Dpn- ML+ Swatch+ KIP+ Blog+ SNB> EZ? FO+ WIP3 Gauge W+ Alt Sw