AW IMR is not protected, it's a safer battery that when compromised isn't as volatile, they will vent. The advantage is they are capable of a much higher current draw, disadvantage is the mah rating isn't as high as Li-Ion.
With the larger sizes like 18650 Li-Ions usually are more capable than needed for our uses unless it's the case of only 1 being used with a booster circuit then IMR is usually recommended. With the smaller
batteries like 14500 which have less current draw capabilities IMR is almost always and advantage, especially when using lower ohm attys.
Super T Manufacturing and Lighthound are great places to check.