Hi @agonzalez ,
if you have the OTel SDK installed into you .NET app, you can set it up to send data to both Elastic and Grafana (I'm not familiar with the details on what Grafana supports, I assume they can receive OTLP), that should work. With this setup, basically all OTel concepts are supported, you can e.g. configure 2 exporters (one for each) in .NET like here, or send data to an OTel collector and push to both via OTLP.
Having our Elastic .NET APM agent and the OTel agent in the same application at the same time is a different story - that depends on the use-case. All NuGet based installations should work with both at the same time, but if you use the profiler based agent, then you can only add 1 profiler for a given .NET app. Our docs can be seen here.
what is preferred way for APM use apm .net agent or opentelemetry?
That's a good question - we already shared our view on this topic here, I suggest you look at that.
any difference in metrics that are collected?
Yes, you'll see some differences and currently our out-of-the-box dashboards may not show data with OTel (you can of course always use custom dashboards) - we are working on that. You can see what metrics the Elastic APM Agent sends out of the box here.