If you're looking for the best flexibility, consider SJEOOW - it features a thermoplastic elastomer jacket which means that the cable remains more flexible than a standard (less expensive) cord.
Nomenclature Key:
S = Service Grade (also means extra hard service when not followed by J, V, or P)*
E = Thermoplastic Elastomer (UL/NEC designation ONLY)
O = Oil Resistant**
T = Thermoplastic
W = Outdoor-includes sunlight resistant jacket and wet location rated conductors (formerly "W-A")
H = Heater cable
VW-1 = Flame retardant
FT2 = Flame retardant
*J = Hard Service
V = Vacuum cleaner cord (also light duty cable)
P = Parallel cord (also known as zip cord) – Always light duty
** When only one "O" appears in a classification (i.e. SJEOW), only the outer jacket material is oil resistant. If two "O's" are in the classification (i.e. SEOOW), the insulation covering the conductors and the outer jacket insulation are all oil resistant
Kal