Ring Sling or Baby Carrier?

[Great Spirit]

Hi. I'm a single mom basically raising my daughter on my own as I couldn't get help from my mom or any relatives. My daughter is now 5 months old. I have a second hand stroller that was slightly used but my problem is that it is so bulky and quite difficult to assemble. I always need to bring the car instead of just taking the train. When shopping, I sometimes need to look for the elevator and wait for it, rather than using the stairs which is in front of me already. I saw some people using carriers and I think that is way more practical. The question is which should I buy? The ring sling which is reviewed here or a carrier which is shown here. Any feedback regarding the use of these products would be highly appreciated. Thanks!