Hi!
I would actually encourage you to go for Cass Business School for the following reasons.
1. UK Program in London -> The UK has introduced a 2 year post graduate visa that can be converted into a Tier 2. If you get a job in data analytics, your role will be on the UK skill shortage list. Therefore, you will be exempted from passing the labour market assessment test. Moreover, the eligibility for UK indefinite leave to remain (UK permanent residency) is 5 years vs. 20+ years for a Green Card in the USA if your country assignment is India.
2. Cass is part of the Microsoft Dynamics Academic Alliance. If you want to get into the Microsoft ecosystem, this is a school where many London-based Microsoft Partners (and even Microsoft themselves) actively target. If you are already part of the greater Microsoft ecosystem, this is a massive plus.
3. Schools in the USA tend to either be National Top 20 or highly regional. Based on where you got admission, I am not sure of the value of the network you would get that would help you get a job in the USA.
For the question of deferral, it would really depends on what you can get as a GMAT score. What is the breakdown of your score? By the way, you probably want to take the offer this year as next year's admission cycle (Fall 2020 application for matriculation in Fall 2021) is expected to be the most competitive of the last 5-10 years due to deferrals.
Good luck!