Dark Angels - 2 Ballistus Dreads Better than Redemptor?

Hi all, new to competitive play and new to Dark Angels. Putting together my first 2k army. I have the usual core of DWKs and ICCs. Still deciding on Azrael, Lion, both etc. But, I'd like my army to have some shooting. In the interest of really understanding what I'm taking vs. just following lists that are out there, I printed off and compared data sheets for four different dreadnoughts: Redemptor, Ballistus, Brutalis, and regular Dreadnought. Some observations/questions below. Appreciate any advice in advance!

Questions/Observations:

  • "Regular Dreadnought" seems uninteresting. Only get 2 ranged weapons. Get a better version of the plasma with the Redemptor and better version of the lascannons with Ballistus. And the Wisdom of Ancients ability seems not that helpful given Dark Angels are so good in melee and I think what I need is big guns providing support
  • Brutalis seems little redundant with all of the melee that comes with DWKs and ICCs. The Brutalis Charge ability seems pretty powerful, but again, I think I need shooting support
  • So this really brings me to Redemptor vs. Ballistus...
  • Redemptor seems popular pick, and looking at the data sheet I now understand why. Get 4 ranged weapons, fairly balanced to take on variety of opponents, Duty Eternal ability adds tankiness (I assume bunch of opponents will try to knock this unit out). In a vacuum, Redemptor looks pretty good...
  • ...but I'm finding myself drawn towards the Ballistus, more specifically, 2 Ballistus Dreads. Redemptor is 210pts, each Ballistus is 130pts so 260pts for 2. So for extra 50pts I get a total of 6 ranged weapons (3 per Ballistus), the lascannons have greater range than anything the Redemptor has (48" vs. 36" for the plasma on the Redemptor), and the lascannons also have greater strength (12) which is good against other vehicles, characters, tanky dudes like Custodes, etc. I lose the D6+1 attacks on Plasma but I get 4 lascannon shots plus 2 missile launchers (1 per dread; also 48" range) and 2 twin storm bolters. The Ballistus Strike ability lets you re-roll some Hit rolls. Also with 2 dreads that's a total of 24 (tanky) wounds vs. 12 for the Redemptor. Again, all of that for just 50 more points.

So, I guess my real question is - am I thinking about this dynamic of 2 Ballistus vs. 1 Redemptor "the right way"? What are some scenarios where the Redemptor is better (or regular dread or Brutalis)? Any comments/criticisms welcome.

On a related note, I'm also evaluating the tanks in a similar way and understand that might impact the analysis above.

Thanks!