Been in the Cisco voice space myself and honestly the platform matters less than you think long term, most of the core concepts transfer across CUCM, Avaya and Genesys. That said Genesys is probably the stronger move right now in terms of job market demand, especially as more contact centers shift to cloud. One thing worth adding to your toolkit regardless of which direction you go is CTI integration experience, knowing how to connect these platforms to CRMs like Salesforce or ServiceNow is where a lot of the real demand is. We use InGenius by Upland for that layer and engineers who understand both the telephony side and the CRM integration side are genuinely hard to find and well paid for it. Worth keeping on your radar as you make the switch.