May - yes. For example, the factory alarm will scare away those who don't expect it, are spooked by a horn going off, and not smart enough to rip the wiring off the horns first. The club will deter those who aren't willing/unable to cut the steering wheel and slip it off. The Mobilistics relay will befuddle anyone who isn't familiar with it, or is unable to swap out the starter relays with the wiper relays that live right next to them in the PDC. Ravelco will thwart the thieves who aren't intimately familiar with it, and know how to defeat it. IGLA will defeat most thieves, save those who come with a tow truck, or know exactly where it's located so they can disable it.
Put it this way - if we compare theft protection to ballistic protection, we have:
Factory alarm -> T-shirt that reads "don't shoot!" - stops the honest criminal
Club -> three copies of the New York Times duct-taped to your chest - stops Airsoft projectiles
Mobilistics relay -> Studded leather jacket - MAY stop a .22 short
Ravelco -> Level IIIa soft armor - will probably stop a 9mm
IGLA -> Level 4 with ceramic plates - will stop most AP rounds
Now... if it were you, and you knew you were going to have to walk into a scenario where people WERE going to be shooting at you... which level of body armor are you electing to put on?