Cisco WLC: Local mode vs. FlexConnect (local switching)

Hi

I'll be inheriting a wireless network with a mix of soon 90 1600 and 1800 series APs that need to migrate from a WLC 2504 to a 3504 due to the older one being out of capacity. Unfortunately the old setup lacks most documentation and has seen little maintenance overall (runs WLC/AP firmware from late 2017) so some reverse engineering and documentation will be part of my job. (there are other things that will be more fun to work/play with as part of that job)

I come with the perspective of Ubiquiti UniFi wireless, they are great in some places but both have their respective places and use cases. But it's obvious that Cisco's WLC provides far more features and tunables than UniFi even at Ciscos lower end.

The old setup uses the APs in local mode, indicating that both management and data traffic gets routed through the WLC currently connected with a single 1G interface via CAPWAP. Technically all APs are on the same site / network, but in different buildings. There is no weak WAN between APs and the WLC where FlexConnect seems to be a recommended scenario.

Coming with my Ubiquiti perspective, FlexConnect with local switching looks quite appealing to me since I don't expect them to buy another WLC 3504 + licensing/maintenance to run in HA mode. Also there is the bottleneck of 1x or 4x 1G in case of the WLC3504 if running in local mode.

FlexConnect could allow this setup to be more fault-tolerant and less depending on the availability of this single WLC? In the UniFi world the controller can die without any significant impact on end users (except when you use their captive portal) which has been quite appealing in previous setup's I've worked on.

I see some disadvantages being mentioned like more complex switch port config more complex (trunk mode) and mDNS limitations etc. with FlexConnect (local switching) but I haven't found any decisive argument in favor of local mode vs. FlexConnect. Maybe I'm overlooking some things that are actually better in local mode vs. FlexConnect / local switching?

I've done some documentation reading but any haven't reached a definitive decision yet.
Inputs or links would be greatly appreciated :)