There was a time when CapEx was the bigger percentage but now with cloud and SAAS services, one should think more about OpeEx. For example things like emails, CRM, office tools etc are easily available on cloud now.

It depends on your industry as well. For example for highly regulated and compliance govern industries its different. You can not have all the things on cloud and hence OpeEx is not always a choice. Yes, but in may small medium industries that is not the case.

Also, OpeEx is always a low cost option, not true. Cloud costs are not cheap.

My 2 cents - For all green field projects - better option is OPEX if there is more of application development as it can be aligned to DevSecOps and Agile ways. Also for brown field projects it is good to go with CAPEX model till the platforms/applications are sunset. The migration cost of brown field projects to move to OPEX model need to be calculated properly

Even in OPEX we need to use the cost optimization models of cloud deployment and have more of reusable components with microservices layer architecture

With Capex you don't only need to develop the application functionality you need, but also infra, security etc. You need a truckload of additional expertise that is not business critical for you. Why?

Clearly Opex is the way to go unless you have reasons not to, e.g. compliance.

OpEx is not cheap always. That is one misconception. Cloud ( SaaS) model is not cheap at all. However, you need a good amount of cost analysis. For example - setting up your outlook server vs using outlook in Azure. Or, using a on prem CRM vs Salesforce.

Here one thing is also important that customization of cloud apps ( OpEx) is sometimes not included in upfront OpEx rate card.