I almost always pair identical primaries together, unless they are in 4:2, like the Myrmidon. Linking identical banks would give me higher dps, and guarantee that the bolt speeds are identical. I hate it when the lead indicator is only for one of the guns, so you end up wasting energy for no hits on one bank at medium range or farther. Unlinking guns works too, but then I'm left with 2 pew pews on most setups.
(speaking of which, I need to go memorize which bolts travel at the same speeds and would make compatible link partners)
Interesting how many people like the myrmidon. Aside from the fact that it carries helios, a lot of people say it's a sucky fighter.
I wouldn't mind it, actually, if not for its huge profile.
Pairing primaries and linking them does not increase your DPS (though it does up your burst DPS which (can be important but is more effective using Prom S AND Kayser at any real dogfight range), supposing you're using Prom S or Kayser isn't terrible but any other weapon combination is an utter waste of time and space)
A few things to note;
The lead indicator being a guide for one weapon doesn't make any difference at dogfight range;
Note for note;
The higher skill level a pilot, the closer the dogfight range will be.
Note for note for note;
You take an Eri, Prom S, Kayser, and Tempest, fire them all at the same time, and basically two shot anything at superduper close range. - You can oneshot some stuff with weaker shields.
There is no other combo. Not for vs AI standard set up, unless you're doing tactical crap (-> Ares/MK2, Maxim, Kayser/PromS, Tempest, Trebuche).
TvT dogfighting at higher skill levels are done in light fighters and is a different kettle of fish.
Linking the same primary weapon with itself does not increase DPS, only burst, and, while it is better than having a singular one because burst > DPS - it's still a waste of space, you would be better off using another gun entirely, for tactical reasons, or increased overall damage.
If you are shooting things at LONG (read, anything over 500-600) range for any period of time you can swap to a single bank if it makes you feel any better, but it's not like it's important then anyway.
Profile is insanely important, many people ignore the fact that fighters (especially the frigging myrm) are almost as big as freighters in profile sometimes!