HRM TRI or HRM SWIM chest strap vs wrist OHR

Really  depends on the sport you are trying to do.

In general OHR is not as accurate as a chest strap and will never be. It is just slower to pick up changes for the heartrate. So in general you could say:

- for activities where HR is not changing much and more or less consistent and not "jumping around" (interval training for example) you will get good  results

- for really hard acitivities or interval training where you peak your HR and it changes a lot, the sensor is just slower and will not really pick up the changes in time, so a chest strap would get you way better results

- weightlifting will also be difficult, because the moment of effort is quite short. Again the sensor will just be to slow and will not pick up much of a change or a change at all while benchpressing or something like that (but HR for weightlifting is not really important for me, so does not bother me at all)

I for myself switch a lot.

Normal running with same pace and quite low effort => OHR (i made tests and the Data for OHR and the strap are really close)

Heavy intervall training  => chest strap

race => chest strap, because of the "peak" in HR Data and it will be just more accurate

for other sports it more or less really depends on what you are doing, i would say use the same logic: more or less steady effort => OHR will do the job   mixing effort => chest strap will do better (especially the shorter or heavier the effort gets).

This is just the general function, on top of that there are some people which just do not have any luck with OHR data at all.... Don´t really know why, but i heard that skin colour, hairs and such can really confuse the sensor and result in bad HR reading. So i guess you COULD have the problem to be one of these unlucky people. But in general i would say "my logic" from above is quite accurate, just make sure that your watch can not move on the wrist and is quite tight. The less movement the sensor will have on the skin, the better the results.