Lob-Star is another fairly complex character to document.  This is because so many of his attacks have dual damage outputs hinging upon his "Boiled" state.

I really like the box-stock aesthetics of Lob-Star, but when he is "boiled" he turns red.  As such, I thought it would be cool to take Winterfet down the Hard Boiled Path.  For better or worse, Winterfest has a unique attribute.  Instead of maintaining the red, or having a tone change, Winterfest turns gold when boiled.  Some will love this, everyone can appreciate it, but others, like myself, will not be huge fans of the "golden" boiled state.  That said, let's take a look at things.

Starshooter is a nice base attack that offers a singular star with quick fire capabilities.  It deals out 25-37 damage.  However, the stars will do 30-45 when he is boiled.  To achieve this state, Lob-Star has to let off steam by holding Attack 2 for roughly 7 seconds.  He can do 3x of 10-15 at the start, and then sits vulnerable while charging.  Once boiled, he can stay in that state seemingly forever as long as you are idle...it also lasts a LONG time if you are just running around (he is significantly quicker while boiled).  When you execute Attack 2 while boiled you can jump the damage from 10-15 to 40-60 3x.

The base upgrades are pretty straight forward.  Interestingly, Sharp Shot not only increases the throwing stars damage, but it also takes the "steam" release from 40-60 to 52-78.  I prefer to call it a "Star Clap" since it seems to be more noticeable than the steam it shoots out.  Boiling Over provides some defense while charging up to boil, but offers no other benefit.  Lob-Star Express takes Lob-Star Roll from 50-75 to 65-97 in standard mode, or offers an increase from 61-91 to 79-118 while boiled.  Executing Lob-Star Express also deals some steam damage at the end of the charge, but it appears to be minimal.

Shooting Star

This is my preferred path for Lob-Star.  It is more simplistic and easy to execute.  Twice the Starpower takes roughly 4-5 seconds to charge and then deals 231-446 2x!!  This was thoroughly unexpected.  Star Defense activates right before Twice the Starpower and runs 20-25 seconds with 3 Stars that deal 33-49 damage each!  I have gotten it up to 27 hits before it terminates.  Oddly enough, Super Stars, the first upgrade down the path, grants increased damage to the base throwing star attack (40-60, 49-73), but only while boiled.  Twice the Starpower and Star Defense do not require being in the boiled state and they do not offer increased damage when boiled.  If you are not "boiled" the throwing stars are capped at 33-49 from Sharp Shot.

I personally would have loved to see Super Stars damage increase apply without having to be boiled.  I also think it would have been nice to possibly just replace Super Stars with 2 standard throwing stars.  I also would have been happy with +40 Armor somewhere down this path.  As is, Star Defense is a very capable defense system.

Hard Boiled

This path is a MUST if you have a strong affinity toward using the Lob-Star Express.  Full Steam Ahead will leave a trail of steam that deals 40-60 damage.  More importantly, this doesn't just impact enemies you are retreating from, but rather you can time the dashes and set up defensive walls to either throw stars behind, set up another dash, or provide a slight barrier to Boiling Over.  Getting Steamed automatically releases steam to damage enemies that hit you, but I could NEVER get a solid damage number from it.  Whatever it is, I don't think it is proportional, and I am inclined to believe it would be minimal at best.  That said, Self-E Steam makes up for it offering increases to the throwing stars (49-73, Clap (78-117), and gives an initial increase to letting off steam and boiling over (10-15 vs 20-30).  Perhaps most importantly, this consumes less boiling power.

If you do not like the throwing stars, prefer the Lob-Star Express take Hard Boiled.  If you are indifferent between the primary and tertiary, be weary that you will want to be boiled at all times with Hard Boiled. If you have a hard time getting boiled without taking damage, I would consider taking Shooting Star.

The Boiler, Lob-Star's Soul Gem can basically go down every time you boil...just hold it for another second and he will jump off screen and then slam down a devastating 400-600!

Conclusion

Personally, for me, Shooting Star just makes more sense.  It is mind boggling why you don't get a non-boiled increase to the throwing star damage with Super Stars, but Twice the Starpower's massive damage output and the sheer (ha, punny!) functionality of Star Defense makes it a moot point.  The way I view Super Stars at that point is simply an added benefit to taking advantage of the speed increase that comes with being boiled.  I will, once again, say that if you like Lob-Star Express, or just find yourself using it the most, take Hard Boiled.  I really would have liked to see an Armor Increase on one of the paths and I truly think Super Stars would be better off not involving the boiled state, or simply granting 2 throwing stars.  That said, either path should make for a solid experience and they are quite different.  Rookies would definitely be better off with Shooting Star and Hard Boiled won't be hard to master...just stay boiled and dash a lot.