Remember that even when you're fighting on an infinite flat plain, you still pay MP to turn while running. Jumping gets you pretty much anywhere within a given radius no questions asked and lets you pick your facing when you land for free. Also, jump MP aren't reduced by heat...
That gives jump jets some use even under ideal running conditions, and in practice much of the time you simply won't have those. I certainly don't put jets on every single 'Mech I use, but for a dedicated close-in backstabber I'd consider them a must.
If only because after my attack I'd like to have a snowball's chance in hell of getting away again next turn, too. :)
Seriously mate, just grant me the courtesy of assuming that I know the ruleset. Facing change rquires MPs, really? :)
Generally getting there to backstabis rarely is the issue, its just that some units are more dangerous to backstab than others (Saggitaire, Pulse Rakshasa, insert your pulse and or flippy arms unit) and its the positioning and timing that makes you go for it or wait another turn.
Heat is rarely a factor. You simply dont overheat on general principle and you are fine. Even in lvl 1 play its a bad habit a desperate gamble if you will most of the time and not an efficient use of your ressources.
Frex. Take a stock lvl 1 Jenner. On turn 1 you get into the rear and alpha. You are 7 heat and 6/9/5 fast. Suppose you fear for your Jenners life and on turn 2 you jump away to cool down. With 5 jump it has to be a location that your opponent cant reach by walking up to the Jenner or out of LOS so that the opponent just can camp and fire at you with their long range weapons at short range. In that turn 2 your Jenner does nothing at all besides init sinking. On turn 3 you are +2 heat and if you found that hard to reach hiding spot you likely have to jump back into the action using most of the available heat sink capacity up and having bad numbers to hit.
Compare that to fireing 3 of the 5 3-heat weapons at the Jenners disposal for 3 turns. You are there threatening everyone within your reach kicking people and never lose a single of those precious 11 running MPs in the process. You still have the option to jump away if things get to tight and if there are no suitable targets but at least you have the choice to do so.
If you want to make your shots count, especially on those 8/12/8s or 7/11/7s then run if there is a way possible. Jumping is only there if you run out of ideas, have to disengage or if you are on the low end of the movement spectrum and unable to reach a safe firing position otherwise.
If you backstab say an unguarded Archer, who cares if you only have a +3 TMM with your Venom when it can only fire its 2 rear medium lasers. If that Archer uses the LRMs its another +2 to be hit. If the Archer doesnt then the Venom took one for the team. 2 Mediums arent going to kill it and preventing dual LRM20s from being fired is great in that case.
Battletech is no rocket science. To play this game well you have to do a lot of little things right everytime you play. A perfect understanding of all applicable rules is a no brainer. If you dont know all the rules in the game then you are guessing and the results will show. You have to know each and every unit at the table. Speed, Weapons, heat sink capacity, weapons placement, which units has flipping arms etc. Of course one can look it up each turn during play. No player I ever played with on table top has the disipline to do throughout the entire game in bigger fights. Its just tedious and disrupts gameflow. Playing a lot makes you memorize these things.
You have to be aware at all times of all to hit numbers of all units around you and their range brackets. There is no excuse for rushing the poor Archer in my example above with say the Battle Hawk starting from range 15 and running 8 hexes towards him ending at range 7 or ending up in a place where say a BHKU-O can run up to you and end in hex 2 range.
Count the hexes, calculate the to hit numbers and lights can be a great asset in a fight. It needs a bit of practice and a feel for the game dynamic.
All the above assumes you use lights to combat other mechs or vees. If you use light mechs only to ini sink, scout (whatever that means in a standup fight) or to fight jeeps or infantry then it really doesnt matter what lights you take cause all of them can do those jobs in one form or another.
About those Sniping Lights (Talon, Jackal-55, etc.):
I am sitting on the fence on those. Experienced players tend to have units dedicated to getting rid of those (Wraith, LPL Lightray or even use the fast pulse Lights etc). The issue is this. You have to get rid of those early in the game to take away the opportunity of your opponent to turn the game into a farce later on. It mostly acts as an insurance that if the game goes wrong that he still has the capability to force you to play out another couple of dozen turns until you are left with no units capable of threatening his sniper.
Eventually taking down an opponents force on 10s when he needs 13s or cant even fire back is a waste of time and the outcome is obvious.
On the other hand those lights give you the opportunity to ini sink, stay away from danger while still contributing to the fight, so they have their merit. But they have to carry a real weapon, not a single AC2 or LRM5 cause those accomplish nothing in the timeframe where your other units are engaged with your opponent, weakened by having BV tied up in the sniper.