Which are preferred contract of EPC or EPCM for successful executing a large capex project?

fixed price vs cost plus, it always depends on the experience on doing the needed project, if a company is having a wholly new type of project, and it could not benchmark to approximate the price, and I believe this would be the case for the contractor, who may opt to provide an arbitrary price, hence, in this case, EPCM would be the solution.

Both are Ok . EPCM is more easy to handle than EPC .EPC is more challenging and suitable for those who revel in challenges