Honestly depends how much random running you do. I had a 245M and moved to a 6 Pro recently and the main thing for me was the routing and nav feature, which if you tend to just do the same routes over is kind of pointless. That being said the cost of the fenix 6 watches is amazing value at the moment as they are trying to shift old stock given the 7 release and for the price/feature ratio its a no brainer really.Been debating if I should get a Forerunner 245 Music which can now be had for £180, or a Fenix 6s Pro for £360. Also seen new rumours of a Forerunner 255, so may wait for that.
I cant see what a 255 is going to add that a fenix 6 series watch doesnt have, maybe touch screen? which is kinda w/e but will jack the price up.