Simple Choice to Essential/Magenta? Also B2G1 question

I have the old simple choice plan and after taxes and fees it's ~$160 for 6 lines. Unlimited everything but only 2GB high speed per line before throttling. It looks like Essential is a pure upgrade and only $135 plus t&f. or Magenta even moreso though a bit more costly at $180.

Any good reason not to go ahead and move to one of these plans or should I go for it?

Also the details for the 3rd line free say pay for two eligible get the 3rd free. Does that mean a 6th would also be free because of the 4th and 5th lines or is it strictly 3rd line only?

Thanks!