Its a controversial question and answers do vary from book to book and obviously its one of the best reasons, why one should not use Indian authors especially, Arihant for ORGANIC.

Anyways, for authenticity, I am giving the stability in terms of thermodynamical parameters from Jerry March's Advanced Organic Chemistry.

Bond Energy(in KJ/mol) of the reaction, R-H ---> R⁺ + H^-

3^o = 970.3

2^o = 1043

1^o = 1316

Allyl = 1070

Benzylic=996

So, 3^o > Benzylic > 2^o > Allyl > 1^o

Probable explanations (red- against stability, Blue- in favour of stability)

Tertiary- High +I effect, 9 hyperconjugative strcts.

Benzylic- Benzene's -I effect, no hyperconjugation, charge delocalisation by resonance

Secondary- Gud +I effect, 6 hyperconjugative strct.

Allyl- little charge delocalisation by conjugation, very less pronounced +I effect.

Primary- Iske baare mai kya kehna.  

Hope it helps.