Not familiar with these watches, but I've got a couple of other "put your finger on the watch" types and NONE of them are worth a darn. Inconsistent pickup, wildly varying HRs, darned unhandy. If you watch the video, they recommend "taking your HR as often as possible" to get an accurate idea of your fitness level and caloric output---that means you'll be running with your free hand on the watch A LOT. Really awkward, and on a bike---forget it!
Just do what the pros and serious folks do---buy a decent HR monitor with a chest strap, you'll see one on every serious triathlete---because they work! The prices are the same! And you get a constant, consistent readout.