Why Quan 1, because that's where the highest ratio of Foreigners is to be found and we all know Foreigners are rich! And easy pickings, too.
Personal security
Seriously, some of the safest places, other than gated communities are in Vietnamese areas - other than Quan 4, where even the VNese get knocked off - because as a Foreigner the watch most everything you do even more carefully than they do their own business.
They know strangers in their 'turf' and watch out for you, once they get to know you. The thieves also operate on the old principal of Don't sh*t on your own back step, which means if you are going to do crime, not around your home area.
Apartment/house security
Another safety item is the front door. Most front doors are an easy out for thieves. They come in generally two flavours (A) a unsubstantial door behind a (very squeaky) sliding barred gate, secured by padlocks; (B) a stout, regular door with locks in it.
The first door type is easy to secure, as long as you don't buy a cheap lock.
The second type is the one that needs work. Accept that VNese locks are, in the main, insecure. There are two locks on the front door of the condo I use as an office: one is a regular 'squiggly' Yale type lock and the other has an impressive 'flat' key with dimples in it.
If the two, the flat key dimpled type is the easiest to open with two very simple devices - a 'L' shaped piece of metal that fits the slot, and a 'probe' which has a small, very square-shaped hook on the end. Most people can learn how within 30 minutes.
The Yale-type lock is more of a challenge. Again specialised tools are required. But the technique, that is harder.
On the door frame I fit stainless steel plates that have holes aligned to the lock 'tongues'. I also had the fabricator put a few tack welds on the face of the plate in front of the holes - which screws up the 'credit card' keys (or very flexible flat metal).
Where the plate bends around the inset for the door and then out in to the front, I had a small diameter stainless rod welded so to stop anything being forced between the plate and the door.
Finally, the plate extends forward so it partially covers the lock key slot - picking requires full access to the key slot.
To make the door secure from both sides I make one of the locks a dead-bolt with a lock on both sides - which means a key is required for exit either way. (This should be left unlocked, or a key left in the slot, overnight in case of emergency). Changing the lock screws, or drilling out the slot, makes it difficult the unscrew.
I also add locks to bedroom doors and any room where there are windows.
Alarms
If you have either money or the ability, fit motion detectors in the apartments/houses. My front door alarm is always triggered when the door is opened, unless I push my bell push before opening the door.
But little beats a nosy neighbour.
Security guards are a risk
Security guards are generally very poorly paid and they supplement their income by renting parking spaces (illegally) to people in the neighbourhood. Non-residents in a building are a security weakness. Watch for users carefully, especially those who park and walk out of the complex.
Personal security
Normal precautions should be taken. Most street crime in TP HCM involves snatching and motorcycles whereas Ha Noi is predominantly pick-pocketing.