You say that, but I find the statement the Reddit might be right highly suspect.
I have got a couple hundred hours into the ME 3 MP, and I can safely tell you, from experience, that Sentinels are awesome, and Vanguards are… Just an excuse to set off migraines or seizures.
They are a one trick pony. You charge in, roll out and charge in again. If you are lucky, someone sets you up for a bionic explosion.
With the sentinel, you have a wide array of abilities, and can set up a wide array of different explosions.
In the single player, its a bit worse, because you want to use cover, and be tactical, but the Vanguard disregards all that in favor of just charging in.
In any case, I am not the only person in this thread with a preference for the Sentinel. I just wish I could have played the Paladin N7 version before the MP shut down. Having that actual shield looked so cool.