Rash said:
On my first few playthroughs I didn't even buy the Striker at all. Just upgraded the shotgun all the way through the game. It's honestly "good enough" for every situation, though the spread-fire capabilities of the Striker are good for someone who struggles with crowd control.
Honestly, this is my preferred way of getting weapons:
-Buy Red9 and stock, and don't upgrade the regular handgun beforehand. Sell Punisher.
-Use the first shotgun all the way through the game.
-Skip the Rifle for the entire village sequence; buy Semi-Auto Rifle as soon as getting to Castle.
-Obtain free Broken Butterfly at Castle.
-Take free Rocket Launcher and use it against Verdugo (takes really good inventory discipline).
And that's basically it. I prefer the Red9 to other handguns because of power and it's general awesomeness. I get that baby to 6.5 exclusive power right before leaving the Castle. I prefer just upgrading the regular shotgun because you get it for free in the beginning and it remains powerful enough to handle situations where it's needed. For my first professional run of the game I used the rifle in the village but afterwards realized that it's possible to skip it and buy the superior semi-auto version at the Castle. As for the Broken Butterfly, its power eventually surpasses the Killer7, plus it's free. The Punisher is the only free weapon that's not worth using, IMO.
That said, everybody has their preferences. I can see why some players like the Blacktail but, I, personally, am all about power and the Red9 is just great.
The Striker actually does more damage than the Riot Gun. Literally, the only disadvantage of the Striker is its cost + you get it late game. It's not like RE5's version, which is less powerful. Everything is better about it except for the one quality that doesn't matter for a shotgun- range. There is really no reason to use the Riot Gun outside of looks. Even the Shotgun has a better Exclusive.
I bought it because it takes up less space and holds tons of ammo over the Shotgun, but generally I stick with an unupgraded Shotgun all the way through until the Striker becomes available.
Similarly, I stick with an unupgraded Handgun until the Red9+Stock.
Toss up on how I'm feeling with the Rifles. Sometimes I go Semi-Auto for speed, sometimes I go Bolt Action for Power. Generally, if I go for Semi-Auto, I skil the Bolt Action. I don't bother buying the Stock for either.
Broken Butterfly is perfect and free, as you said. Insane fire power. The Killer7 has a better firing rate, but again firing rate is worthless for a Magnum where you have limited ammo. Make every shot count.
As a general policy, I never use a Rocket Launcher in a playthrough unless I'm messing around with the Infinite Rocket Launcher. I grab the one that's free and sell it for cash.