Space Wolves armies have access to a wide and varied selection of vehicles. I'd like to discuss all of these options and weigh up the pros and cons of each. Starting with the Dedicated Transports, bear in mind that unlike other Space Marine armies we are only able to use Rhinos, Razorbacks and Drop Pods. The Land Raider is only available for a single squad of Wolf Guard (although in fairness you're unlikely to use more than one because of their cost). Before I start discussing the vehicles themselves let's look at the upgrade options:
In summary, don't bother! With the possible exception of the 10pts for a multi-melta on your land raiders, they're really not worth the points. All of them are very situational and, considering the most common vehicle in most armies is the Rhino, they're overpricing a cheap vehicle. Some people take extra armour but I really don't see the point. All of my vehicles are vanilla and unless I read something very persuasive I can't see that changing.
The humble rhino is the workhorse of any Space Wolves force. You're unlikely to see a list without at least a couple of these (unless it's a drop pod only force). The rhino has a capacity of 10 models which makes it perfect for squads of Grey Hunters. Bear in mind that if you want to include an independent character in your squad you'll have to lose a squad member so they can still fit.
The rhino has pretty basic armour at F11,S11,R10 but that extra point on the front and back can really make the difference as it means a minimum of strength 5 to cause you any problems. The low price tag of 35pts makes it an obvious choice and the included smoke launchers are essential in it's role. I nearly always drive it forward at full pelt in the first turn then pop smoke and ride out the fire. Sometimes launching the smoke is enough to make enemy players ignore it completely.
One thing I've learned recently is that if you moved then don't bother getting your troops out. If there's a very small weak target that you think you can rapid fire to death then maybe give it a go but otherwise I prefer to force my enemy to de-mech me and then make him wish he hadn't. If he fails then on your next turn you charge him and we all know how that ends.
Very similar to the rhino but you pay 5 extra points to equip it with twin-linked heavy bolters. Then you can spend another 35 giving it lascannons or the often used las/plas combo (which the new models don't have in the box). The trade off is that you can now only put 6 models in there. Personally I prefer larger squads but I occasionally take one to support my long fangs. Essentially they provide you with some cheap (if flimsy) long range support which is often missing from Space Wolves armies. Some people have discussed the idea that twin-linked ACs are better than the lascannons and whilst a lot of the time they're better against high toughness the ability to cause instant death is lost and high AV vehicles will be pleased to see you've not got the las. They're the same points so I'd say stick with the lascannons.
The Drop Pod
I really like the idea of these things, causing havoc as you drop your troops (or dreads) in behind enemy lines. They can certainly be a nuisance to destroy as they're AV12 all the way round and are great in objectives games. There are two fairly large problems though. Firstly they have to use the Drop Pod Assault rules which sees the majority of them coming in on turn one. A good idea on the surface but since your enemies entire force will be pretty close to where you bring them in, the occupants are going to have to survive a torrent of fire. Secondly, you can't assault straight out of them which means getting out and rapid firing then weathering a turn of enemy shooting/assaulting.
That said, I still like them and I'd love to one day field the majority of my army in them. They're a nice safe way of deep striking your troops in and in fact they're the only way of getting terminators in by deep strike.
The Land Raider
If the rhino is humble, the land raider is nothing of the sort. One of the toughest things to take down in the game with it's AV14 all round. Any enemy who doesn't have melta will struggle as even railguns will only penetrate the armour half of the time. They can fire an extra weapon most of the time and any troops inside can assault straight out of it even if it's moved.
You do, of course, pay a hefty price for this. At around 250pts it's difficult to justify taking one at anything upto and including 1500pts. They're the same prices as a fully tooled up Grey Hunters squad with a rhino for example! That said I love the feeling of deploying one of these bad boys and filling it full of Wolf Guard terminators with an array of nasty CC weapons. If you're going to take such a squad the Land Raider really is the only option as it guarantees to deny your enemy the charge which can be crucial with all the Furious Charge thats going around.
The difficulty is that they're a massive target so you're never going to hide them. Yes they can take a lot of punishment but they're certainly going to attract it and you still have to be careful to steer clear of melta weapons. There's nothing more disheartening than losing your mighty raider to some poxy little lascannon and it's a real blow to lose such a big chunk of points.
In summary then, the transport I'd use most would be the Rhino as it has a clear role even in low points games. The others are by no means useless though, and I think a mix of them will help keep your opponent guessing.