Introduction
Let's start by saying that I want to provide some more in depth data about these gun lines as they fulfill a similar role and share a similar playstyle.
From my understanding the general consensus seems to be that all things being equal, the Blasters are slightly better than the Antiguas and while I was a little skeptical since my reference was the 4 star Blasters vs the 5 star Antiguas, after getting Riftlocker and Arcana to level 10, I sort of made up my mind and now I am also fairly confident in saying that the Blasters are a bit better. I'll provide some more detailed feedback on how these guns feel to me so that other players can discuss and provide additional information so that people on the fence about these guns can make their own judgment more informed.

I'll provide data about these gun lines for depth 25, 26, and 27 with damage bonus maximum and at heat level 10 unless otherwise specified.
Fun fact, 5 star Blasters require to be level 9 in order to be better than their fully levelled 4 star counterparts.

I don't play PVP so my considerations will be just for PVE.

Obsidian Carabine and Valiance are excluded because I don't own them.

About the charge attacks
The charge attack of Blasters is essentially worthless. Two basic shots will outdamage a charge attack in the vast majority of situations, and I'm fairly confident that the charge time or heck even the animation time alone of the charge attack shooting is longer than shooting two basic shots. A positive is that the charge attack has more flinching power at least, though I fear it's not enough to justify using. Besides this, the actual charge attack is fairly unremarkable in the sense that it works as you'd expect and oddly enough doesn't really have a bigger AoE compared to the normal shots despite the bullet looking very big. It also features massive knockback for some reason, so be mindful of that.

The charge attack of Antiguas is actually not really that bad but instead of being worthless is just impractical in most circumstances due to leaving the user rooted in place for the whole animation without the ability to even change direction. It has the added gimmick of the bird projectile having one of the if not the longest range of all projectiles in the game, so I guess it can be used to hit some distant targets that otherwise would require a pot, though don't get the wrong idea its range is nowhere close to vials and said pots.

In short these two gun lines have pretty bad charge attacks as far as I'm concerned.

Normal shots
Pretty much all that you're going to use with both gun lines. I personally go for bursts of two shots with Blasters while with Antiguas I basically spam basic shots with reloading. Basically it's run and gun until all enemies are dead.
Blasters have a magazine of 3 shots compared to the Antiguas' 6, though of course a single Blaster bullet is stronger than a single Antigua bullet.
Blasters reload time is fairly slow while Antiguas have one of if not the fastest reload speed in whole game, hence why with Blasters it's really a good idea to use the "shoot everything but not the last bullet" strategy.
If a target has a particularly short vulnerability phase, it may become convenient to shoot 3 Blasters shots. With Antiguas you'd probably want to use a charge attack but chances will be that you won't be able to pull that safely.

For Blasters specifically, there's a pretty noticeable difference between the 4 and 5 star versions mechanically. The 5 stars have what I feel like is a bigger bullet size and this means that you're going to hit targets more consistently and in a slightly wider area. All gunners know that a good amount of times bullets will display a hit animation but the monster takes no damage whatsoever (especially in motion) and while I cannot 100% guarantee that's the case, the 5 star Blaster bullets seem to be less affected by this when compared to their 4 star versions. It's also easier to hit two targets that are close to each other therefore adding that pinch of extra AoE, which is a nice extra.
Riflocker in particular seems to have an easier time hitting beasts compared to its 4 star version.

Using Antiguas right next to a block will have weird detection issues where you'll fire the shot but the block will still stand unscathed, though I'll let the reader decide how much this is important. I think it's a small minor nuisance, but you sure do get annoyed when it happens.

If you opt to use the bursts of two with Blasters they become a little safer because you don't reload and therefore have more chances to shield.

Thinking all 6 Antigua's shots will always land is pretty optimistic; thus I think it's worth considering the cases with 4 and 5 shots landed.

Antiguas feature no knockback whatsoever while Blasters have a small but non negligible amount. I'm slightly in favor of the Blasters here as it can mess some monsters attacks by altering their position but it's nothing major.

I'm actually incredibly conflicted on the actual attack speed of both gun lines relative to one another; I have genuinely no idea how many Blasters bullets you can shoot during an Antigua 6 shot "combo", but I have the subjective sensation that two bursts of two shots for Blasters may be kind on par with a full Antigua "combo". I'd greatly appreciate data on this aspect as I hate having to time stuff like this.