Vantage M3

In my experience Precision Prime is way better than Elixir. I returned my M3 for that reason.

This is in line with my observations. Polar Precision Prime is better than Elixir (Pacer Pro better than M3, in my case). I'm glad they went for Precision Prime on the new loop band. Garmin (various watches) was almost always worse than Polar Precision Prime for me.

I think if you dig in my posts you could find a few detailed comparison answers.  I personally would stay away from Run, as it’s a different underlying platform from the rest of Suunto family and is thus incompatible with many Suunto features like S+ apps. Moreover, it seems it was more of a one shot attempt at alternative to the development that started with S9PP and isn’t going forward. Race S is a great watch though, which brings me to my next point. V3 is more akin to Race, so your real comparison is down to S vs M3. Both size, screen size, weight, and price wise.  Sleep, recovery, and general activity tracking is absolutely better on Polar assuming you can stomach their embarrassingly outdated app. They promised to overhaul it next year, but for now it is ass ugly and keeling over. That said Polar does have a web version (Suunto doesn’t anymore), with tons of useful reports and features. Also included are several adaptive fitness programs, from their  running programs to FitSpark to paid Fitness program. I think their training load and training load status are far easier and more intuitive for most people to deal with than Suunto’s stuff licensed from TrainingPeaks. On a flip side, Suunto has a very gorgeous and super informative app with ton of features (and sadly ridden with many bugs) and many great watch features targeting more advanced users, from ability to import workouts from third party systems, to track running mode, to structured workouts targeting specific intensity ranges not just plain 5 zones like Polar, to ZoneSense, to climb guidance, S+ apps and device integrations, and so on. I believe Suunto and Race S do have an edge for more training and fitness oriented people.  Getting to things like accuracy I’d say Suunto owns Polar on GPS (M3 is quite decent but not as good as Races). Also Polar tends to do some weird altitude thing that results in elevation gains 20-30% lower than other watches. On OHR, it’s the opposite. I find Polar far more stable and accurate. If you care about heart rate, unless you go for the latest gen, you’ll want that chest strap with Suunto for sure. Accidentally, Race S is better than other Suuntos, but far from perfect.  I’d say if your focus is more on general wellness and activity tracking and your fitness needs are generally to support that, M3 will be a great choice. If you need something sportier and with more advanced modern day training features go Suunto.  One other consideration is Suunto does update their watches with new features regularly (like 3-4 times a year) and does so for years. On a flip side, those updates lately bring unwanted bugs like HR dropping out in the middle of an activity, sleep tracking not working, etc.  Now my personal solution when faced with a similar dilemma?  I have Vertical 2 on one hand and Polar Loop on another. I do have V3 too for morning orthostatic, jump, and VO2 Max tests and a few other things Polar does well.   It’s either that, or get a single Garmin really… 

Also glad for my M3, light, good battery life, discrete, same software as V3 etc.

As a polar vantage m3 owner I'm hoping this means some polar flow updates to support the new fitness band. Also hoping it can be concurrently used with a polar watch so I can wear my nice watch on non-workout environments while wearing the hand on the opposite wrist. Polar needs to survive the review onslaught though for me to consider buying it though.

If your primary needs are; sleep tracking, training/exercise programs/suggestions and recovery tracking, then Vantage M3 beats Race S/Run by a long shot. It is not even close.