If you get a top shelf Suunto, you will get better battery life and maybe slightly more accurate tracking (not sure on that). Other than that, the Garmin is leagues better in every conceivable way. Suunto support is the worst garbage I've ever had to deal with. If you have an android phone I wouldn't even dream of buying a Suunto watch.
Right now I own a Garmin Fenix 5 and I am very happy with it. All functions work, including sync, without my intervention. I've had it about 9 months. Before that I had a Suunto Ambit 3 Peak Sapphire. It would never sync automatically, had to be re-paired to my phone constantly, and had known bugs preventing me from using the training plans feature for running for years. A fix was never made. I accidentally left that watch on the top of my car and never found it again. Good riddance.
Seriously there is no comparison, and with Suunto going down the touchscreen route with their new line and ruling that out, you just can't compare them at all.