TLDR BP is better because it gives Vit, Dex, Elemental Damage, and CDR.
A perfect CoE is 200% damage for 1 of 5 elements. In U6 your only real damage is Cold, and in R2 Generator it's basically all Fire. So 20% of the time you do triple damage, 80% of the time it's basically worthless. That's a net 40% damage upgrade overall for two common specs, which isn't trash by any means.
BP has a ~77% chance to activate on 5 hits (the odds of not critting 5 times in a row is .955). That's a really tough number to turn into an effective CHC. In something like U6 you can estimate it saying you launch SSS every 2 secs and it takes 1 sec to complete and you never attack with 100 Fists (which is not how it works but for the sake of modeling it let's say that) then you will do 14 hits after every 3 second cycle starts. You should hit 5 normal hits and then 14 crit hits for a 74% effective critical rate when it works perfectly. 16% of the times you'll hit a 4 normal and 1 crit which pushes back the streak 1 to 4 more normal attack and tries again, and so on. I haven't taken a stats class in 15 years so I forget the exact formulas to sum that sequence but since even the "fail" streaks where you don't miss 5 crits in a row includes a crit by definition, then you'd thing the effective crit rate has to be around 60%.
That's for a specific scenario that doesn't exist because you have to 100 Hands to maintain Focus/Restraint. You also can "fish" for the streak to ensure 100% of your EPs are crits, but that creates downtime where you're doing nothing and squishable. In Generator build your attacks are a little more evenly distributed with no waits, so it's smoother. Let's just say 50% of your SSS attacks are crits and 60% of your Cripples are crits, which might be way off but it's something to work with.
The real benefit of BP though isn't the CHC, it's what you get instead of the CHC on gear. Having 50% CHC is basically mandatory, without crit you just are gimped. It's normally at least 5 times damage (+400% is not difficult to get when you're getting 260 from weapon gems and 50 from paragon, let alone gloves and the potential 200 from jewelry) and if it works half the time...you just can't pass up a 2.5 damage multiplier, that's more than Focus/Restraint's 2.25. With +400% CHD every 1% of crit is +5% to damage, which is an insane value.
BP's advantage over CoE is that you gets other stats because you aren't stacking CHC on all those slots. That's things like 1000 Vit on Helmet, 1000 Dex on amulet, 10000 Life per second on Bracers, 16 CDR on rings, etc. That's a lot of benefit with a lot of stats provided, especially if it gets you CDR on gloves and rings or 20% elemental on Amulet. Those stats can combine to trump the 40% damage on CoE.
So in the end, BP is probably better on a spreadsheet but both are really streaky in that sometimes they make you a beast, and sometimes you're sitting around for 8 secs wondering why this elite isn't dying because you're on the wrong element or you keep getting those random 5% crits and ruining your procs. BP has the fairly awkward drawback of making your gear designed to support a mechanic that doesn't work at all without the setup, so if you want to loan those items to another character and it isn't using BP than you're missing all that nearly mandatory CHC on gear. If you don't want to mess with setting up all your gear to the BP build a CoE ring is not terrible, just not optimal.