Which project is better in SAP FICO?

In both these types of projects SAP FICO plays big role and it's implemented from scratch or new functionalities are taken into account in case of brown field.

Well it's a pretty difficult thing to answer. I can share some insights into kind of projects which are prevalent in industry where SAP FI/CO is relevant. FI/CO plays a big role in almost every project barring some.

When it comes to implementation projects, there are 2 types of projects generally i.e. Greenfield and Brownfield. Greenfield are those where SAP is implemented from scratch and Brownfield are those where there happens migration from old SAP to new SAP. In both these types of projects SAP FICO plays big role and it's implemented from scratch or new functionalities are taken into account in case of brown field.

Other types of projects include roll outs to different plants, post implementation support projects, implementation of other modules which may/ may not have integration with SAP FICO directly.

All projects provide opportunities to contribute and to gain significant experience generally however many consultants prefer to be part of implementation projects which offers much wider scope because of the nature of the projects but there are challenges too. At times people are on their toes in implementation projects and it brings good experience which is beneficial in all types of projects so do look out if you can part of an implementation project.