Aizen B6: why is it so good?

Hi everyone

Im pushing pushing for Aizen B4 right now and was wondering if its actually worth to go for B6, and wanted to ask how it actually work/how much it actually improve his dps

I'm asking this because i dont know if i misunderstood it, but as it is, its a 2x crit rate (only with battlefield skill, so hado 90 and i will stand atop the heavens), and any extra is converted to crit dmg..

So in reality, we Get (i will use my stat as example)

39% crit rate + 37.5% from weapon = 76.5% crit rate

180% crit dmg base + 40%+86% from urahara (215% crit dmg) = 306% total crit dmg

B6 Aizen should give 2x 76.5% + 153% / so 53% more crit dmg (for a total of 359% crit dmg)

So if my battlefield skill deal 1m dmg, with crit it became ~4m dmg (1m base dmg + 306%) / and with the A6 it only become ~4.59m dmg (1m base dmg + 359%)

Did i Get it wrong? If its this way, i dont think its too worth for an A6 and i will probably stop now at A4, cause it should give me around 11% actual dmg