I have a sealed sword capable of turning into either sword, but im not sure what ones better.
Divine Avenger or Gran Faust?
These are totally different swords. While they are both slow swords based on the sealed sword, they do different damage types. The Gran Faust does shadow damage, and the Divine Avenger does elemental damage.
Get a Gran Faust if you want a sword that is strong to gremlins/slimes, neutral to constructs/beasts, and weak to undead/fiends.
Get a Divine Avenger if you want a sword that is strong to undead/constructs, neutral to fiends/slimes, and weak to beasts/gremlins.
Otherwise, the swords are pretty dang similar. If you don't have an elemental or shadow sword and like the slow swing, then get both. Which to craft first would depend on what you want to kill faster first.
Im going to make either one so i want to know the more powerful one. The best generel damge dealer.
it does the same weak, normal, and specific damage. it's really up to what kind of monsters you would be fighting.
Thx dude. Im looking towards fighting Slimes and Construct a lot.
That doesn't really help. Da for constructs, and gf for slimes.
If your primary monsters are slimes & constructs, then either weapon works since neither will do weak damage against them.
Get DA if you want to do more damage to constructs than slimes.
Get GF if you want to do more damage to slimes than constructs.
Also of note, DA doesn't curse you on the charge attack, but the GF can curse enemies on second swing or charge. Personally, I'd go with the DA only because I think constructs are harder than slimes and I'd rather be able to charge without a chance of cursing myself.
If you want optimal attack against both, then you need 2 swords (one of each, or one of the two plus some other line of sword). You can read more about damage types on the wiki and you might want to read this sword guide - http://wiki.spiralknights.com/Swordmaster_Guide
As others have said, Elemental damage is better against Constructs and Shadow damage is better against Slimes. If you didn't already know that, learn the matchups:
http://wiki.spiralknights.com/Damage#Monster_Resistances
To decide on which damage type to go for, you should probably consider what other weapon(s) you will be using it with. Asking which to go for without providing such information is asking for lengthy explanations with lots of qualifiers. If your other equipment and the places you like to dive do not help you in choosing between the two, one thing I don't see brought up enough is that the Faust's user-curse capability allows you to share heat with friends at the end of a run. You pass on the Avenger's really nice charge attack for that capability, though.
Okay ill get DA because i need more help with constructs than slimes. So ill just get DA.
You should also look at the charges. Personally I find DA much more useful because its charge sends out three blades that can hit multiple times and push back enemies. I find the GF charge unusable not because it only shoots one huge blade, but because it can curse you, and I have no curse resist equipment.
If you want a weapon to fight constructs and slimes, get the DA. GF is better for slimes overall but the charge attack is almost completely unusable (insanely long charge time plus self-curse). Meaning that you'll be stuck using the normal swings forever.
DA, however, is a great weapon. It's better for constructs (which are more worrisome than slimes, as Nordlead pointed out) and its charge attack (initial swing + 3 holoblade projectiles) is so powerful that it ends up oneshotting slimes anyway.
Hope this helped.
Needs more info. Like what are your other equips and what do you normally do (JK, FSC, etc.)