You cannot compare share prices and make the statement that one is at a premium to the other simply because one's price is higher. You need to understand valuation.
On a market cap basis (# of shares x price) HTZ is almost 5x+ the size of CAR-Crash: $6.3B vs $1.3B.
But in terms of valuation, HTZ is trading at 12.2x 2012 EPS and 10.3x 2013 EPS, while CAR-CRASH is trading at 7.9x 2012 EPS and 7.0x 2012 EPS. Thus, HURTZ is actually trading at a 50% premium!!! That is what you ought to be asking.
Perhaps the answer lies with "who has the stronger balance sheet?" CAR-CRASH's is, in my opinion, filled with smoke. Take a look at tangible book value - CAR's is negative -- by quite a bit.
Ask yourself which company you would rather buy if you could buy the whole shootin' match.
Hertz has announced that they are rolling out car sharing to their entire fleet by July 2013. This can dramatically reduce overhead costs as rentals become self service. Avis, on the other hand, is sleeping at the switch and has only committed to 30,000 cars by that time even though the Avis solution is hands down better than the Hertz solution. Hertz also has an entire division working on smartphone apps to enhance the rental experience. What is Avis' counter to that?
So in this case, I blame the go slow Avis management. They can be leaders, but they choose to lag behind and play "me too"