That is a good question to note.
The CBS250 series are Layer 2 and basic L3 switches whereas CBS350 series are advanced Layer 3 switches. That means we have incorporated in CBS350 a certain number of enhancements and value-added features in terms of security, manageability and PoE budget compared to CBS250. From a functionality standpoint, key differentiators are PoE budget, Stacking and some advanced security features like BPDU guard, Dynamic ARP inspection, sFlow, RSPAN, etc.
Based on your use case as an A/V integrator, I suggest you won't need those security enhancements but will be more focused on the management and PoE options and least but not last the price. That being said and if the PoE budget satisfies your needs we would recommend the CBS250 series switches. Also do not forget you get the new Cisco Business Dashboard embedded within the switches which as part of the Cisco Business Dashboard app give you a great opportunity for centralized single-pane-of-glass view, monitoring and management solution to your or customer's network. With Cisco Business Dashboard (free for download) you can manage up to 25 devices free of charge with no license.
More detailed information about the product and how to set up you can find in the following links:
Cisco Business Dashboard (CBD)
https://www.cisco.com/c/en/us/products/collateral/switches/business-250-series-smart-switches/nb-06-bus-switch-trans-guide-cte-en.html (scroll at the end to link to the datasheets)