This is anecdotal from browsing vagabond sources, but there's a lot of reasons NYC might have fewer homeless.
A) The pigs and rules on the east coast are a lot more brutal towards the homeless than the west coast. This both leads to migration away from the east coast and for the homeless that are there to be much more invisible.
B) The west coast has a history of being relatively welcoming to the houseless / a lot of lore built up around it, so people tend to gravitate towards it.
C) The west coast has a much more survivable climate than the east coast - this is the reason I hear the most.
As a local, I'll add what I think are more meaningful differences.
First, most homeless people in CA are locals who were forced out, not interstate homeless migrants looking for a good place to be homeless.
The main reason is that CA doesn't have nearly as many temporary shelters for people to go to. And as you noted, it's more survivable to live outdoors.
Overall, NYC still has a pretty big population of folks in shelters, but CA has way more folks living in cars, trailers, and tents.
The article says that Los Angeles county has 75k and the city has 46k. As for population, NYC has a population of 8.8 million and LA city has a population of 3.8 million. This means that NYC has a homeless population percentage of 11.3% and LA has a homeless population percentage of 11.9%.
It's probably a bit of an apples and oranges comparison, NYC is split into the five boroughs each of which is its own county. Some of the boroughs seem to have radically different homeless situations, some being as low as 1000 homeless persons. LA (city) on the other hand is approximately 45% the population of NYC and doesn't take up it's entire county, but has nearly the same homeless rate.
At the same time Los Angeles seems to run into other towns and be nearly seamless with them. Should Anaheim get lumped in with LA? If we're counting those should we expand NYCs area to include Yonkers and Newark?
NYC doesn't have as bad of a homeless issue as LA.
Because you'll literally die the very first winter night you're homeless without shelter in NYC. They have a bunch of shelters, so the problem is less visible, and when they run out of space they bus them to L.A.. Those that remain are found frozen to death in the morning.
NYC also has a roughly equivalent homeless population to LA, but LA has less than half the population than NYC.
Being a NYC native, I can agree that if the situation definitely is not visible. But considering the population differences, I'd say it's not as bad in NYC.
Bronx has a median rent to income ratio of 45%, while Manhattan is 30%. This is primarily due to the fact that median income for Manhattan renters is double what it is in the Bronx, but rent doesn't scale up the same. Against my own expectation, this makes Manhattan a reasonable-ish place to live, at least if we're just talking about rent and income.