Well, they both carry about the same missile load. IIRC, the Redeemer carries 20 S2 and the Vanguard 16S2. Not sure how many launchers the Redeemer has. Could be it can only launch 2 at a time. Could be at times the Vanguard has the missile advantage and it can carry S3 missiles. I don't think the Redeemer can do that, and they haven't updated the ships page so it would take ages to find what they plan.
The Vanguard is a multi-role platform, modeled after the P-61 Black Widow radar equipped Night Fighter, and F-111 Aardvark fighter-bomber. To get the most out of it you'll need 2-3 players, but it can be handled with just 1. The Redeemer really needs three players to take advantage of the guns. It is more akin to the AC-130 gunships. Expect it to need more power, glow brighter on sensors, but have perhaps a third shield. I think it doubtful it will be stealth capable. Many ships are not. I would not be surprised if it is faster in space than the Vanguard but handles poorly in air. Same manufacturer, so we're expecting different trade-offs. The Redeemer does not have a good airframe. I'm guessing they are building them to be primarily Intended for the Interceptor and patrol roles, like the Skipray Blastboat--more than a match for most fighters. Hope for a third medium shield if they go that route.
The Redeemer was my favorite ship for a long time until I realized that we really want to optimize firepower, maneuverability, defense, etc. all over crew. Think about three guys in a Redeemer against three guys each in their own Vanguard. . .and well, the Redeemer looses. Badly.
Think about a small team doing a terrestrial incursion, and the stealth in the Sentinel frame with the bang of the Hoppy mod wins easily over any other ship yet proposed.
Maybe, if you don't care about stealth, and you know you have three guys, and you want to take just one ship for some reason, maybe the Redeemer is a better option. Only Maybe.
Plus if you want group play, there will be many Sentinels with Harby mods teaming for long range stealth strikes. You'll always be able to find solo or group gameplay killing Vanduul. It's hard to see it now, but long range is going to be a huge advantage. For solo bounty work, probably nothing beats the Sentinel with the EMP if you want them alive, and with the 3XS5 when it doesn't matter.