Working with 2D Vector logo's for 3+ years now I would have to agree that Adobe Illustrator is the current industry standard & more than likely the best choice if you have the budget for it. However, I must also point out that while I do own Adobe Illustrator CS3, it's more of a backup & conversions software for me.
My Primary Vector software is still Serif DrawPlus X2 (3+ years using it). There are several Vector software's you can use to produce the same results, it's all about 1.) what software interface you are more comfortable with, 2.) Your investment budget, 3.) And your primary clients requirement as far as extensions go.
Just to name a few:
Adobe Illustrator CS4 - $499.00
Corel CorelDraw X4 - $429.00
Serif DrawPlus X2 - $99.99
InkScape - FREE OpenSource
As you can see, you have options from FREE to High end. The main difference for prices in Adobe & Corel draw as far as being way more expensive than Serif is that Adobe/Corel software's are hacked more & have a larger overhead to cover, thus a higher price to compensate (Common business practice).
At any rate, those should give you an idea anyways. Good luck to you
