I recently came across this question and really liked it quite a lot. It made me think of my own pets and how they correlated to different stages of my life. While I have not nearly covered every aspect of owning a cat or a dog, I did manage to come up with a few distinct points. One thing also dawned on me, the only way to answer this question is by posing even more questions :)
Are you someone that likes to interact with people, or are you a little more reserved?
Dogs require walking and by nature they attract quite a bit of attention. If you have a dog complete strangers will start talking to you about your dog, the dogs they have had, what breed your dog is and all sorts of questions regarding care taking as in what you feed your pupper to how often and long you walk him/her.
If you have a cat, random people will not walk up to you for a conversation. What often happens is that you will announce you have a cat in company because you will have the odd kitty hair clinging to your clothing, also, other cat owners will recognise this and ask if you have a kitty yourself :)
It’s not to say that cat owners are less social, there is a whole online world that is absolutely crazy about any and all cats! It’s just that you won’t get stopped in the street.
Are you home a lot or do you travel?
Doggos are real companions when you take trips and are on the road a lot, it’s great to have their company, their little friendly fluffy faces greeting you - always. If you are more into taking trips that require airplanes, it gets complicated. Often a kennel is the solution, or if you’re lucky you might have friends and family that would love to have your fur monster for a few days or few weeks. It’s not a problem, just one more thing to consider.
It’s a little less work for cats, they are often completely fine with being alone at home for longer periods of time. Organising a neighbour, friend or family member to come around to feed and provide fresh water for your furry kitty is not nearly as taxing as asking someone to house your dog. Just don't expect a warm welcome when you get home, often cats are not impressed that you left them, they will let you know this by giving you the cold shoulder - I seriously recommend coming home with a variety of kitty treats.
Another question for you is your health, how is it?
Dogs need walking everyday and a few times per day. If you are not able to do this you might have a problem. Having said this, if your health is not stable there are ways around this, dog walkers and often times family and friends are more than willing to jump in and get their daily exercise by walking your dog. It requires more effort though and if you are already a little sick, it might add a little too much pressure to an already difficult situation.
Cats on the other hand, are not so needy in this way, they are highly independent creatures. They do require, love attention and affection and playtime is always much appreciated! Daily walks in all weathers are not an issue though.
One more thing to keep in mind is that cats live an awful lot longer than dogs do, some can reach double the age of a dog. I met someone the other day that has a cat of 21 years, she’s a little less active and a little deaf, but otherwise she is a fighting fit kitty cat.
While caring for a cat or dog requires different approaches, ultimately they need your care, your time and your dedication. You must be grownup enough to meet their needs at all times as they are completely dependant on you. If you are not able to take responsibility I recommend getting a few of these:(exclusively sold online) You can always get a dog or cat afterwards when you’re ready for one, they’ll love giving these toys chase :)
Good luck with your choice!