We need to review our security strategy.  Currently we use a service provider to provide SIEM and SOC services.  They use Manage Engine and OberserveIT. They also patch and upgrade our endpoints. Tend Vison one is the foundation on which we have built our endpoint protection.   With all the new Microsoft Security products and AI on offer  (A) should we replace or augment? (B) What do you use to Administer the landscape from a single pane of glass. Both out Trend and managed Security Service Contracts are due to expire. (C) what gotchas do we need to lookout for if we decide to replace / retire any of the existing tools in our environment.

THREAT MODEL! 
Nothing ever works if you dont have clear picture of potential threat areas! Start from there and then explore tools in market that offers the closest. Or work with existing vendor and ask them to provide a detailed threat assessment and current coverage!
all the best!  

This is a good chance to reframe your operating model with service providers. 
Create a list of key performance and risk indicators that you/your CEO/your board will be interested to see. Identify source tools / technologies where you can grab data for each of these KRIs/KPIs. Then, hand it over to your SIEM/SOC service provider, for them to provide those to you in the form of a CISO dashboard. You should optimally not care about how they grab and correlate those KRIs whether using manage engine Microsoft Sentinel etc. if you own the security tools (like TrendMicro, Manage engine etc.), you should look into options of changing them to either inbuilt into your licenses (like MS E3, E5 etc.) or change them into a subscription model. Make your service provider own the tools as much as feasible while you only define your needs from them.