Opinions vary quite a bit. Maybe people who like to design that stuff can chip in.
Since the fight often starts at long range, long range weapons can be quite good. Just as important to the range itself is the range brackets. The Light Gauss Rifle, a much maligned and ignored weapon, has fantastic range but that's not the point, its range brackets are great, making it a more accurate weapon on average regardless of whether its long range or medium range.
Since the tendency is to start off at a distance, detect each other, and then turn in for the merge, the range tends to close fast. So true "fire support" platforms loaded up with LRMs and little else practically need an escort. By the same line of thinking it can be useful to add 2 fire support platforms to a squadron mostly considering of medium/short range brawlers.
Today in a lot of ways among the heavy fighters the Eisensturm is the gold standard in terms of firepower and armor and it can dogfight too. But you pay to have all of that in one platform, it's an expensive bird. The Omni is like 22 mil, the non-Omni version is like 17 mil.
In new heavies you see a lot of somewhat-copied Eisensturm's now. The FWL have one in the Shikra, the Combine has one (name escapes me). These are great airframes for both space and in atmosphere they can practically do everything but be an interceptor.
But again you are paying a lot for that. For that kind of cost you buy 2-6 airframes of something else that's cheaper.
So at least in terms of firepower and armor and speed, for heavies, look to the Eisensturm or Shikra as good benchmarks in multiple areas.
I'd also touch on a few pieces of equipment that are great.
1. Chaff pods/AMS- Lot of ASFs flying around with the air-to-air version of the Arrow IV missile under their wings, same with dropships toting missile systems like Barracudas designed to shoot down fighters. I personally love that the Shikra has chaff pods because downing a Shikra with an Air-to-Air Arrow IV is definitely worth it to an enemy. AMS also great for same reasons. Some other ASFs have worked on other solutions, the Poignard carries a small pulse laser for anti-missile work.
2. ECM- I didn't appreciate this for a long time, but in the game rules an ASF carrying ECM effectively is granted bonuses akin to cover with ground units (so harder to hit). Since the only cover around may be the cover you bring with you and bubble yourself in its definitely worth considering. That's why you see a splurge of new ASFs equipped with ECM as of TRO 3085 or so. Dropships produce a much better ECM bubble and sometimes in space I'll pair a squadron of ASFs with a small attack dropship (e.g. an Avenger) whose primary function is to be the moving cover bubble.
Armor has gotten a lot trickier now because we have different armors. Some are better at absorbing laser damage versus ballistic.