Bear with me... (feel free to correct me on anything)

So I've decided to go with 30-06 due to availability and versatility. Someone mentioned bullet grain which as far as I understand higher grain=more stopping power.

So here's what I'm gonna do

Buy something bolt action, chambered in 30-06.

Any reason I shouldn't, let me know now. Also can someone please explain caliber system to me.? I don't know what's stronger 30-06,or. 308 and those are the 2 I'm focusing on.
Thanks for answering my stupid questions