Lost between Asterisk and CUCM what to chose?

Hi,

I'm looking for the best option for me between Asterisk and Cisco Unified Communications Manager (CUCM). They both have advantages and disadvantages.

My number one priority is: I'm willing to build my own SIP trunk line and apparently Asterisk and CUCM are both able to make SIP trunk.

The advantages of Asterisk :

1. Free forever
2. Good Design and modern UI/UX
3. More popular (If I'm not wrong)

The advantages of CUCM:

1. Very full (not sure if Asterisk have the same amount of conditionality)
2. Could create SIP Tunk and SCCP, DID, much more
3. Certification CCNP (350-801)
4. Used by large businesses

Downside:

1. Not free 60-day trial and hard to know the price for CUCM 12.5
2. Old UI and not user friendly
3. Made for Cisco phones

Note: I'm taking the training: 350-801 with 300-070

I'm new to the world of telephony, so if I'm wrong in a place please correct me. If I missed something please correct me.

For now, I don't have many calls, but in the next few years, I will probably become a SIP trunk provider.

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Finally, which PBX Should I choose between Asterisk and Cisco Unified Communications Manager?

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Thanks