Oil versus gel is the first decision in full-contact massage: oil keeps a trace of friction and belongs to body-to-body, gel erases friction and defines nuru.
Every full-contact technique needs a medium between the skins. Two dominate. They look alike in a bottle and behave in opposite ways once warm.
Massage oil is a plant oil or a blend of several: sweet almond, grapeseed, jojoba, fractionated coconut. It spreads thin, absorbs gradually and leaves a small, controllable drag. That drag is useful. It lets a forearm hold a muscle for a moment, lets weight keep its position on the slope of a back, and lets the therapist read tension through resistance. Oil is the medium of body-to-body and of erotic oil massage. It stays on the skin until soap removes it, and it marks cotton.
Nuru gel is water-based, made slippery by an extract of seaweed, clear and without scent. It does not soak in. Friction falls close to nothing, so contact turns into glide and one body crosses another without catching. The price of that is control: weight cannot be parked on a slope, and the film dries at its margins and needs water to revive it. A shower rinses gel away without soap. It is the medium of nuru.
Choose oil for pressure that can settle and work on a muscle. Choose gel for motion without resistance, and only where a shower is close at hand. A nut allergy matters with oil, since almond is common; name it in the first message when booking. Long hair and pillowcases generally fare better with gel.
Cost plays no part in the decision, since the two techniques share one ladder. The guide on oil, weight and glide compares them at greater length.