I think you should get BH because as you said, and I quote'I'm leaning toward silversix, because I normally use elemental weapons more than shadow'. For the reason that you use elemental more, you wouldn't have to worry a lot about retrodes, but you still have the problem of gremlins, which isn't solved.

Choosing between different damage types isn't really something you should be doing in my opinion. If you need a source of Elemental damage, take an Elemental weapon. If you need a source of Shadow damage, take a Shadow weapon. If you need both at different times, make both and take what you need when you need it.

Unless your Antigua has an amazing UV, in which case analyze what kills you the most. Enemies can be annoying in different ways, but if they annoy you in ways that don't involve your death then it's not all that important.

If you don't have the great UV, consider getting both. And at the end of the day, just get what makes you happy. If you really want to pick off Gremlins, get a gun to pick off the Gremlins. Optimal equipment isn't as important in this game as we're inclined to believe.

It's not so much a question of getting things now as what your plans are. You need weapons to be able to take care of every enemy in the game, so plan to get them. Personally, I have exactly nine pieces of 5* equipment at the moment: four weapons, two trinkets, helm, armor, shield. I don't need a lot of extra equipment because I picked a setup that covered all the important bases. If you didn't pick as "perfect" a setup (which is fine, there's nothing wrong with wanting to have a little variety in your gameplay), then you'll need to spend more money to get what you need. 'S how the game works.

Plus, who knows when the damage change is going to happen. I don't know if it's a great idea to plan on getting one of these guns and leave yourself without a key piece of equipment for who knows how long. But a slight bonus vs gremlins in the now may be okay anyway. Or upgrade your toxic cata to a biohazard, which is a perfectly fine shadow gun in its own right. Or get an an umbra driver. Both good shadow guns.

You're still low star in your equips, so it's really not a big deal for you to just change paths entirely. It's only once you get to 4* that you're really locked in with the investment.

But yeah. You're going to have a DA. You don't need any more elemental damage. Go for shadow, whether it's your future biohazard or the sentenza.

The only enemies weak to shadow dmg that does not dodge bullets are the slimes. And elemental guns work fine on slimes as well. I see no reason to get sentenza at all. To solve your gremlin problem, get a shadow sword.

The problem with getting a Sentenza now is the money, though. Namely the fact that you'll have no weapon that's good against slimes and you'll have to get one. Although you can probably make do with the DA.

If you really enjoy using the Antigua, upgrade it to a Sentenza and use it on gremlins. Having weapons that you enjoy using is way more important than anything else. I'd be a little wary of the fact that it only gets a 25% damage bonus and not the full 50%, but I can't say how much of an effect that has since I don't use one myself. If you DON'T like using the Antigua on gremlins, and you don't want to get a Biohazard or an Umbra, then by all means go for a sword instead.

Sorry if I'm offending you; I'm really just trying to give you all the information you need to make a decision on your own. At the end of the day you can work with whatever equipment you pick provided that you have some idea what you're doing.

Here's your weapon lineup:

Snarble: Good piercing damage; sword. Check.
Avenger: Good elemental damage; sword. Has a ranged charge attack. Probably best weapon in the game. Great in FSC when you go. Check.
Toxic Cata: Shadow gun. Can't hit gremlins. Use for slimes, still need a weapon for gremlins.
Sentenza: Semi-shadow gun. Good against gremlins, could be useful against Alphas too if you're not liking the Snarble on them.

Shockburst: Elemental sword. For pvp, I'm assuming.
Lightning Cap: Shock bomb. Also for pvp.

So with that you've got all the bases covered. If you don't actually like some of those weapons, then definitely don't use them. And it's pretty clear that you're going to need to go Sentenza with the Antigua rather than AP to cover your gremlin weakness. That's really all I've been trying to tell you.

@Project-Ray Just a minor note, you may want to revise your "lightning cap for EVERYTHING" after trying to use it on a tier 3 gremlin bomber final arena wave, and turning the entire screen into a carpet of explosion.

http://img14.imageshack.us/img14/9924/spiral20111111151352.png

In my defence, it seemed like a good idea at the time.

Of course i have tried... -.-

Its just that guns suck against gremlins.

We used one revive. I got blasted lucky with both the menders saying "Mend!" and some of the bombers saying "Catch!".
It was fun, thanks for reviving my memory of that photo haha.