I already unlocked the HE cannon, guess it's too late to really ask this. But I had a lot of certs and I needed something to play if I was PO'd at the cheese. Should I stick with the HE cannon or go back to the Viper? I did have some success with the HE today, but I am a terrible driver so I got rekt by some vanguards pretty quickly.
weapon selection is situational... Viper for mixed infantry/armor HE for those infantry zergs that happen when the defenders break out of the base and start chasing your forces back to your base
The Viper can 2-clip a Liberator, or 1-clip an ESF, so 2 fairly accurate Lightnings can shoot low and slow airplanes down. The HE Python, I have some doubts. On the other hand the 75 mm has really small splash damage, forget scoring kill assists by firing through windows. It all depends on the targets.
I love my HE lightning setup. It is great against infantry since it will 2 shot just about anything if you are a few meters off. When used as an offensive artillery on towers/sunderers. You can rack up nice kills. It is viable vs other tanks but obviously AP is better. I like the HE and have never used Heat. I go AP or HE depending on what i am hunting... good luck!
I would say they are each better in different situations. If you are hanging back and shelling, HE is better and you can sort-of snipe at longer range with it. Viper is better for closer ranges and for spamming at faster moving targets and/or shooting while moving yourself, since it gives you more room for error with the 6 rounds.
Viper is all around better, HE is for laughs when you're bored and want to try out hard mode. Its like using an ancient catapult! Still works, but it doesn't really excel at much. You can easily snipe infantry with the Viper from ranges where the HE will struggle to hit them.
Even with a fully kitted AP Python Lightning, you're still going to have trouble against MBTs. But an HE Lightning will win against a Viper 9 times out of 10. The Viper has driver has to land all of his shots to win. It's easy enough to dodge half of the shots it spits out and drill it with HE. Once you get good with the HE, it does much better than the Viper against infantry. Most infantry don't expect you to one shot them faster than they can pop off a dumbfire and get cover, but the HE will do it all day. Slap thermal vision on that thing and you're ready to go harvesting.
I prefer HE for the ultimate in cheese mode infantry farming. Single shells mean I don't have to compensate as much for recoil or target movement, and it is also far easier to fire through those small windows into buildings where infantry like to cower in fear. The OHK on direct hit is really important as well for those occasions where you won't be able to rely on splash, most notably when your targets have the high ground. The only downside to the HE in my opinion is the lower bullet velocity. At times it will feel like you're shooting out wiffle balls rather than tank rounds - especially if you're shooting at longer ranges with zoom. With practice though, this downside can be mitigated quite a bit.
I find the Viper really good at mopping up infantry and it's decent for scaring away low flying ESFs and other air. Never used the HE, my other gun is the AP Python. This will get an ESF smoking with 1 shot and can take down enemy Lightnings pretty quick, especially if you target the rear of the tank. If you see an enemy Vanguard, get out of your tank and run away. It doesn't matter what you are using, an enemy MBT will wreck your Lightning in seconds. It's a bit silly how unbalanced the Lightning is compared to an MBT.
I use both, generally depending on which I need kills on for my lightning directives. You don't need to bail out of your tank to escape MBTs- one of the tricks to good lightning play is to operate in areas that have friendly vehicles (MBTs, Sundies) and use them as cover. If you get shot at, run away past friendly vehicles- most MBT drivers will stop shooting you to shoot at the MBTs & Sundies that they don't have to chase down. Lightnings are the tank in which you should be cherry picking which engagements you know you can win, and using hit & run tactics. One user posted a good lightning guide somewhere in which he basically says that your lightning should never be the first vehicle the enemy engage- even if the area is empty, don't sit around and occupy that area waiting for the enemy, because you want the enemy to engage friendly sundies/infantry/mbts before you engage them. Vulcan Harasser's however, there isn't a whole lot you can do about them. They can outpace you and will happily focus on that lone lightning over the MBT's & Sundies.
I prefer the viper for the fear aspect. If feels like mortar fire when you are on the receiving end. It is also generally a better all rounder than HE.