So generally the pro of coreboot is that it is open source, but the con is that it is open source.
What I mean by that, you can fix any issues yourself, however, if you are unable to do it yourself, you have to wait until someone does it for you and often what features are available and stable are a hit and miss.
Compared to proprietary bioses, the company has some kind of standardized process for developing the bios. So you often get want you would expect. However, if the money flow from the pc vendor to the bios vendor drys up, you, or the community of owners. will not be able to fix any issues.
Linux support should be the same, regardless if you choose proprietary or open source bios. But that depends on how well the coreboot was ported to the platform. So officially supported coreboot bioses are likely better than others.
Personally, if all other attributes are equal, would go with coreboot, because I like to support vendors that offer that choice, and IMO a open source solution, that you can review and build yourself is intrinsically more secure than a binary blob, where you have to blindly trust some corporation. But other security minded people might disagree, which is fine.