LB-10-X's only have the cluster effects over UAC-10's (and the weight) and this is an MBT so the ability to double tab is probably more useful (or viewed as such by the designers, remember this is a Lyarn design)
LBX fire's a bit more effective than ultras against other vees, and there's the TH bonus against flyers to consider (specifically VTOLs), then, there's the superior effectiveness against grunts and suits as well-not MUCH superior, but still, the difference between popping ONE or TWO infantrymen in a hostile platoon, and dashing out up to ten of them? And there's the crit-seeking at, say, other tanks to consider as well-most vees still crit-out before you can hammer through the armor, an ultra gives you a single "2" cluster roll, whereas an LBX can spread the luuurve and disable enemy vees at superior ranges.
Then again, I'm a guy who, when he pulls the trigger, wants the gun to fire-even if it misses or does a reduced total quantity of damage. Ultras lay down a lot of hurt-assuming that they actually DO fire-but having a gun you can't use even when you're close-to-full on the magazine? Worth less to me than the other option.
for Canon designs, I tend to favour the base-model Patton (3025) simply on account of knowing that the gun will, when I need it, work... and the ability to go 5P/10S for ammo loadout isn't that bad, imho.
As for the LRM rack.... best loadouts are, unfortunately, optional rounds- Smoke, Incendiary, Thunder or T-Aug. Dropping smoke covers your approach, or retreat (or just manuever), if you're using fires rules, incendiary works as terrain-denial for certain units, and generates smoke, and the "Mine" rounds can stall or chew up an enemy thrust at your flank if you do it right.
In general, the Patton is probably the most "Conventionally formulated" tank in the game-that is, it balances on the three axes of Armor, firepower, and speed. Most heavies sacrifice on speed, which is a mistake unless you're fixated on pillboxing early with your tank units. 4/6 is the "floor" for a good tank-you can move and turn and climb hills without going flank, at a reasonable pace, your TMM ends up being equal to or better than your penalty for movement.
Tanks are "Team Player" units. If you're trying to "Duel" with them, you're doing it wrong and deserve what happens to you, a lance of Pattons works to support each other, and it works as a "Point man" tank for a mixed lance of similar vehicles in the 4/6 bracket, (based on ammo choices, of course).
The 3025 variant, with the right ammo selections, is suitable for use against 3085 and better opposition (when used correctly). The "Upgrade" is more specialized, it's not as good an MBT, but does include more MG goodness to keep close-in enemy grunts off your decks (or to sweep the decks of a swarmed comrade.)
The nice thing about a Patton chassis, is that if you want to run it in formations with Rommels, Rommel Gauss, and Manticores, it fills a good niche, if you're using it as the bruiser for a "Medium" lance (say, Myrmidons and Bulldogs) it fills a niche wihtout falling out of formation due to being too slow to get out of its' way (like the Axel, the "Utter FAIL" member of the family, unable to climb a hill without being damn-near immobile to an enemy gunner).
Aesthetically, the Patton (and cousin Rommel) has something else going for it...
It actually LOOKS like a Tank, not a bit of skateboard art puked out in Kalifornia.