In my experience if you're looking for a particular/specialty brand, size, etc then online can be a very good way to go. Places such as Discount Tire Direct has free shipping. 4wheelparts has free shipping/freight almost every weekend.

Basically the positive side is that you don't have to pay tax and any disposal fees or other tire fees are already calculated into the price. No real negative side in my experience. I've ordered my last 3 sets of tires online and have saved literally $100's.

On the other hand, if you're just looking for some stock 235's or a no-name brand doesn't bother you, go local. Just remember to take taxes, disposal fees, etc. into consideration. In this case, I usually just call around for prices before I go anywhere.

You'll have to pay for mounting and balancing regardless. Certain places, such as Discount Tire/America's Tire offer free lifetime rotating and balancing standard with their installation- regardless of where you purchase the tires.

Sometimes it can be complicated choosing which route is best b/c local stores will give you either a total 'out the door' price or one that doesn't even include any fees; make sure you ask. Online stores however will give you a total price at the click of a button.

IMHO by how you describe your tire search you're probably better off going local but it doesn't hurt to check online prices just like you'd call around before just going to one place.

It never hurts to check the local classifieds and eBay as well. Of course if you go eBay, try to stay local. I managed to get a set of 5 brand new 31x10.50 MT/R's for $500 picked up off of ebay! That's over $250 in savings if bought today; I saved over $300 when I bought them 2 years ago.

HTH

~R