Should I get one for locking onto air or ground. Which is better in your opinion. Also what is the HP amount for each type of vehicle? And will I be able to shoot "dumb rockets" from a locking one?
Go with decimater for close up fights (court yards etc) and annihilator for long range with good visibility. If you play TR, go with Striker instead of annihilator. It's basically a better annihilator. You won't do much damage with annihilator/striker solo, but when there are 3 or more of you, you'll be able to deny armor and air in a big area if you got the visibility.
As a VS I'd recommend the cheap AA lockon for most people, dumb fire for maxes and vehicles while locking on air.
Default works rather good. Decimator makes vehicle catch fire with 1 less rocket than default one. It will not kil ZOE MAXes. It does as much damage as titan AP and I have been hit by one of those shells when using ZOE and survived, not using kinetic armor. Lock-on launchers does a little less damage but I don't know if it makes a difference but it's nice to be able to hit tanks from afar. The AA launcher can help with scaring away pesky ESF that keeps annoying you.
If you are TR, the very first thing you should save up certs for is the Striker. Its one of your most important weapons. Also, since you have a VS on Waterson, feel free to message me in game if you have any questions about PS2. I'm always trying to help new people with the game. Oh and I am your Vanu Queen on Waterson. Personally I can't wait for the Mentor Program to start.
They will, which will allow you to dumbfire against infantry and tanks with the AA launcher... and will still do equivalent damage.
Air lockon takes a while to set on smaller vehicles and all locks as well as missiles in flight are negated by one flare or the ESF just flies away (I kid you not). Its OK vs Liberators or Galaxies. Render range on very low settings mean the ESF can pop in, attack and pop out of your render range in less time it takes you to lockon. My HA uses the SKEP launcher and Grounder RL's. They're OK but its rare to actually make a kill since it takes such a long time to reload and lock on and an engineer easily repairs any damage you can do to a tank. None of the RL's are any good solo tbh unless used vs infantry - I use mine all the time vs infantry and have tons more kills against them than vehicles. (ballpark figure of 5 infantry to 1 vehicle).
I consider the ESRL (Lancer/Phoenix/Striker) to all be pretty darn good, but if you are going for the budget version, go for the G2A launcher (250 certs locks on to air) as it's the only way for normal infantry to effectively engage air threats.