As for the Good / Bad. The S2 is way more user and application focused. There are more applications available for it, but most apps on the Samsung store are developed by 3rd parties. And Samsung really doesn't seem to have any type of Quality Control on the apps posted, and as far as I can tell, no refund policy.
There are some very useful free apps and themes, but most have a charge ($0.50 -$3.00). With that said, you don't get free trials, if you buy it, it's yours no matter what, garbage or not.
Battery life is hit or miss. Compared to something like a Fitbit Blaze, it's outright dismal. Depending on usage, apps, and screen settings, expect 18 - 28 hours on a single charge, compared to my wife's Blaze, which can go 3 - 5 days on a single charge.
The application integration (reading and responding to emails, SMS messages, phone calls, alarms) is good with a Samsung phone, but with a Pixel, I dont know how well it will work.