Serpentine belts are used in new vehicles due to the fact that they are easier to maintain and are less complicated to install. V-Belts are still used on the majority of the older, classic motors. Some simply like the style they give or having each of their accessories run on their own belt. The deep V of the v-belt can help guide the belt back into place if the alignment is slightly off. And with being a smaller size belt the pulleys tend to be on the smaller side, making things a little more compact. They can be used in any orientation - vertical, horizontal, etc. But they can't handle the higher RPM's and cannot be used for long distances because of the weight per unit of length. And if one belt does end up slipping off the others could keep your engine going for a short amount of time until that first belt causes the others to slip as well. Not to mention that the location of the accessories and pulleys gets to be pretty complicated on most engines making it more of a hassle to change the belts when needed. The thicker multi-rib design of the serpentine belt provides a better belt to pulley contact ratio that creates less slippage. With most serpentine systems only using one belt there will be less distance between the accessories, simplifying the engine compartment. They use proper tension with the help of the tensioner. The serpentine belts tend to be easier to modify because you only have to remove the one belt. The main downside if you do decide to do a serpentine conversion the brackets and pulleys need to be made for your specific engine model. It's not a one size fits most kind of style. Which can be annoying but that means the engine in your car could very well be one of a kind. Both of there belts are good in their own way. Not one is truly better than the other. What it really comes down to is your preference. And what style you are trying to go for. If you are looking to do something more on the interesting side and want to make people think how in the world did you do that, or you want to keep the original style. And you are not afraid of a little extra maintenance work then v-belt would be your way to go. But if you're looking for something new and that offers a little more. Something that is also on the easier side to maintain, a serpentine belt is what should be going on to your engine. 
Power Steering V-Belt System Replacement for Ford 390 427 428 FE Engines with Ford Power Steering Pump : Automotive
CVF Racing Carbon Fiber with Black Diamond Finish Serpentine System for Small Block Ford - All Inclusive - PS & ALT-CF-BD-302-WRAPTOR-PS - Rod & Custom Motor Sports
SBC Wraptor Serpentine Kit - All Inclusive - Alt Only - Electric Water Pump - Affordable Street Rods
Chevy Small Bock Serpentine Conversion Kit - Alternator & Power Steering Applications : Automotive
CVF Racing Serpentine Kits, V-Belt Systems, Brackets, Pulleys and Hinges for Ford, Chevy, Chrysler and more.
Serpentine Belt 35 inch K080348 Special Order CVF Racing 8 Rib 35
CVF Racing Engines, Winter Haven, Florida
CVF Racing K080392 Micro-V Serpentine Drive Belt Length 39.87
CVF Chevy Big Block V-Belt System with Power Steering, Electric Water Pump - Polished
Guide to V-Belt Selection and Replacement
CVF Racing V-Belt System, AC, Alternator & Power Steering, For Ford 351C, 351M & 400, Kit
