...Ahhh. One of my favorites at last!
The 'G' is a nasty opponent - in the -3N (note I'm reading from the original 2750), the design protects a solid 3rd of its firepower in the torsos, while keeping the longest-ranged weapon and a pair of secondaries in the arms with the widest possible arcs. Being able to fire the Lgl and the 4 MLs while Jumping is a bonus, and the 6-P could be used for only a slight heat increase or substituted for the 4th beam, so the Guillotine has a bit extra crit-seeking ability.
This isn't a knockdown-fighter, its a bodyguard or attack unit to hack at an opponent's armor again and again until bigger guns open a hole.
Frankly, the -3N is my favorite classic. Its tough, hard to hit the weapons through the heatsinks, and while it packs a light weapons load for a Heavy its going to use them for a while. The -5M is my favorite 'modern' variant - the ER-Lgl is the logical weapon to add a bit of advanced technology. Its the -3N all over again. The -8D marks the high point of the design improvements, but the strain to keep cool makes bracket fire necessary and takes away some of its flavor. I would have preferred increasing other aspects to create a cavalry unit, adding MASC, replacing the 6-P with 2 4-P (ST), and keeping the rest of the -5Ms weapons while making the arm-mounted MLs Extended Range weapons. Fortunately, that's what HMPro is for.
The -4L is a slight dumbing down of the original - the loss takes away the ability to fire all 4 of the MLs and Walk while adding its only real danger; ammo explosion. It takes away some of the original's zombie-like charm, and makes it harder to deliver the sanding to an enemy's armor that kills it. That said, I've seen worse variants.
The -4P is the weakest of the bunch; with only 10 tons of armor, the -4P sacrifices a bit of endurance in exchange for a bigger, better, gun. Its best used to keep enemies with similar secondary weapons at range - bodyguard duty or fire support again.
I'm not personally familiar with the -6WB or -6WB2. The -6WB would probably use the H-PPC and LRM for bracket fire at range and keep the ER-MLs in reserve for a closer-ranged flashbulb, while the single ton of ammo makes me think Thunder rounds would be preferred for the LRMs to better keep enemies from closing. The FF, compact gyro, and small cockpit seem in line with the traditional roles, helping it stay in action longer and using the C3i to assist in targeting. The -6WB2 is more a cavalry unit, I think. Its a bit puzzling that it uses I-JJs to boost its jump radius (thus speed), but uses paired L-PPCs and a Light Gauss Rifle as its main weapons. Frankly I consider this a deliberately flawed design, and the fluff about attempting to confuse opponents with such a radical change so much nonsense. It should be considered as an separate design, but I wouldn't use it given a choice.
I won't go into the Clan IIC versions.
Overall, I curse that it was produced by Irian in the FWL. I would far prefer it be produced by the Davions or the Marion Hegemony, my current faction, but I'm still happy to see it widely available.