CR-1 is cheaper.
And once you enter the US you'll have right to work, travel and GC in hand. You'll be better protected as an immigrant too.
K-1 is longer if you consider entire time to get GC. You will be restricted more, unable to work or travel outside the US for 6-9 months. Also, if your fiance changes mind and doesn't want to marry you, you'll have no path to stay in the US and generally will have fewer rights compared to LPR when entering on CR1. Not to say this is a major item, but there's nothing wrong in choosing the best for yourself.
Of course, the trade off is temporary separation while waiting for CR-1. Though, if you happen to have visitor visa before you start going this route (I-130 etc), then you most likely will be able to visit the US. And of course, your fiance will be able to visit you at your home country.