LOCATION
Most people I talk to prefer malls for the same reason that Willie likes grocery stores. A grocery store might actually be better DEPENDING on the location. As long as the location is actually inside the building. And not in the open right by the entrance. Some ATMs have a booth with doors.
Best to avoid the ATMs on the street. I used them just fine but I was careful to make sure no body was watching. Basically it was on a major street but during the day and nobody was in the immediate vicinity hanging around. It also had a privacy booth. On top of that, there are some in Poblado right by the tourist police stand. Not saying the police will do shit, but probably a bit tougher for criminals than some random ATM.
WITHDRAWAL AMOUNT
For me: I want to minimize trips for safety, but some do it for cost too.
I looked at all of the options and
Davivienda was the best option for me. The most money for the lowest costs. I could pull up to +1M COP each day and double that on Fridays, though of course I spent way less than that. This meant I could do one transaction instead of sitting there doing 3 transactions like at BancoColombia. I ignore fees since my bank covers them but this may matter to you.
Minimizing trips and transactions lowers the number of trips and time at an ATM. In-and-out. It's over real quick just like when I fuck 9/10s

. That being said, I was carrying a bit of cash on me and that is it's own risk. You have to do your own math as to what you want to risk more. I preferred more cash for less time.
For me, the cash was just prepago money anyway so I didn't need to go as much as other people. I used card whenever possible because I wanted to have cash only for when HAD to use it. This also lowered the number of trips I needed to take. Loutron & La Isla did take card though and when I went it was the same price no matter how you paid. That may be different now.
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A couple caveats that you may already know:
1 - Regarding Davivienda: people complain that sometimes no money comes out. I never had that problem, but it is not rare either. If this happens there or at any ATM, keep your receipts and your bank will reimburse you. It is common enough where your bank should have dealt with this before.
2 - No Matter what bank you use: ALWAYS DECLINE the conversion. The ATM/Foreign bank conversion rate is a ripoff. I'm not talking about the fees, as your bank will probably absorb those.
I'm talking about the actual exchange rate here. You want to use your bank's rate Schwab/Capital One/Chase all give you the interbank rate. People think that hitting decline means no transaction. This is how they trick you into accepting their B.S. rate. I mention this because this is like getting robbed. Over a few ATM visits they might get more out of you than a thief would hahaha.
HOW LIKELY YOU ARE TO GET ROBBED AT AN ATM
Not sure but I'd say higher than average. I'd probably just go to a mall ATM now.
But you still have to make sure nobody is watching. They don't have to follow you. A lookout can snap a quick pic and text a buddy outside. Or he can signal another guy to follow you. This is probably paranoid but if I was a thief this is exactly what I would do. Especially because if somebody hit the ATM it is a guaranteed score. Plus they still get your phone, watch, chain, etc.