This topic has been an ambiguous issue for many who want to do company registration with Corporate Affairs Commission. I will just go straight to the point:

Business Names are cheaper to register. This is because of lesser documentation that is needed during registration, and no stamp duties charge as well.
Generally, with a budget of N20,000 or less, you can get this done without sweat.

Limited Companies are costlier because of more documentation, need for professional services and stamp duty charge that will be paid to the Federal Inland Revenue Service (FIRS) during registration. You will require the services of a professional here to file in as your company secretary (a requirement of Companies and Allied Matters Act 1990 as amended), or you might get stuck during the registration.
This will usually cost you around N70,000 for private company (LTD). I do not recommend PLC for startups.

Incorporated Trustees. This category includes NGOs, churches and religious organizations, every non-profit business. Now this involves newspaper publications along with other requirements. You need about N150,000 to get one registered.

You may check here: https://www.nairaland.com/3369172/tips-getting-business-name-approved for tips on how to get your business name approved.

As an Accredited customer of CAC, I answer questions and provide assistance if you have issues with registration, for free.

Now concerning the duration of the registration process, this can now be done in less than 1 week for both business names and limited companies.
Non-profit organizations will take more because they require 2 weeks notice to be published on newspapers. Total duration should take about a month.

Here is useful information concerning how to get a name reservation without stress
https://www.nairaland.com/3369172/tips-getting-business-name-approved

Hello. I have issues with name search. They kept denying my requests. Its a business name.
Can you assist?

CAC generally enforce strict rules in reserving names for a business name when similar names already exist. You are more likely to get denials than if you want to do a limited company.
My advice:
Go to PUBLIC SEARCH on the CAC website and search for the name. If you see other companies registered with similar name then yours must be different from theirs by two words. Or better still, think of another name altogether.

Need more info? Call or WhatsApp .

FYI. If you need to contact me directly, call, text or use the telegram messaging app only