YC or Heavybit is generalist has a some strong content with playbook and so but will take a 7% (if I'm correct) of your capital for YC and I think 700K for HeavyBit.
An angel typically will put between 10K for small ones to 150K for big ones with big names and network taking way less capital and having actionable insights / network.
Angels are people not institutions and are more willing to help on a daily basis using their names and leverage their network putting their reputation or time on the table because they believe in you VS a YC where you are 1 among thousands and YC depends on who you have to manage you. Ive heard they have an amazing content and network, they have a strong branding, YC brands will help you hire, market your product. but it's more a factory while Angel are more the expert / goldsmith.
YC and VC (in general) are shares driven requesting X% of your capital in general while angels and heavybit are money driven asking to put a certain amount of money without looking at a minimum amount of shares this money would represents (again it's generalist)
Both/Three are complementary bringing different things on the table.
Personally invested in AI, Fintech, InsurTech, Quantum computing.
Started Small helping a friend of a friend with his AI startup (my expertise) and ended up investing in pre-seed.
Then a guy who was also an Angel round also in the pre-seed started a company and ask for my expertise on tech in general (like guidance around architecture and later ML/AI problems etc...) => they asked me to get into their pre-seed.
Then we got along well and started creating a syndicat of 10 people : bringing each other the smartest people we know that were willing to invest/get involve into our syndicat.
Then invested In companies : founders liked the value => some of them joined the syndicat later
each year we would open angel "applications" : all of us bringing the smartest people we know with different expertise (startup specialized lawyers, social network specialist, retail, online distribution, fintech, web3, infrastructure, product management, etc...)
Also everyone has it's own network which make this tentacular very quickly and Founders LOVE this as it's helping them to accelerate super super quickly.
we are now 30+ and it brings even more value and speed/faster time to market to founder.
Local/close to founder expertise => global impact that the job of the BA
my twitter @jilijeanlouis if you want to DM me.