Twin-linking isn't a great idea for commanders since they already have a high BS and access to special guns.
However, regular squads of "Deathrain" battlesuits (Crisis with TL missile pods) are quite effective, particularly with Targeting Arrays (or Target Locks)
Twin-linking is a good idea for standard suits. Twinlinked BS3 is more reliable than BS4.
Arming philosophies for stock suits and commanders should be looked at differently. The commander has a wide array of special weapons, gear and hardwired options.
for your commander, hardwired multi-tracker is almost mandatory. If you want to save some point, taking an 'El instead of an 'O works out to be almost the same effectiveness if you give him a Targeting Array.
three weapons is almost never a good idea as you can only fire two with a multitracker. Fusion guns are tempting, but if you take one, make sure you give him a shield and maybe some stims since he'll have to get in dangerously close to use it.
Single weapon suits can have their uses. It frees up a slot for targeting arrays (twinlinked BS4 meltaguns or missile launchers or plasma guns can all be handy), or Target Locks. A squad of crisis suits with TL fusion and Target Locks can play merry havoc with a closely grouped unit of tanks. Or shield generators to aid in survivability.
The key is to pick your role and arm accordingly. "Fireknife" (plasma and missile) is good for hunting light armor and even heavy troops. But if you want a specific role like tankbusting, twinlinking a single weapon system is often the way to go. For troop hunting, it largely depends on what kind of tropps you;ll be facing. Burst cannon and flamer. Twin flamer, BC and plasma, even plasma and missiles are all good anti-troop options of varying intensity.
I guess the boiled down version is that twinlinking is handy for standard suits, kind of a waste for commanders. As to what and whether you want a TL weapon or two and a multitracker is down to the role you want the suit to fill.
