Given the two choices definitely a morning person. I hate to waste the day and as long as it's light out I am awake and raring to go. Of course I get an extra boost from my large mug of coffee.
I'm 100% night owl, but my circadian rhythms still vary widely so that my sleeping and rising times aren't consistent. I was very happy the 17 years I worked nights but really suffered when I switched to days. If I had a 3-day weekend, or a vacation, I was already switched back to night owl before it was over. I'm a firm believer that days should not begin before noon, and then only gradually.
Definitely night owl. But of course I have to get up at 6:30 for work. So I drag all day until about 7 pm, then I'm raring to go. Then I get busy doing stuff so I stay up too late, so I'm tired the next day, and so on forever. I really need to put more effort into resetting my sleep cycle so I'm not so tired during the day. My ideal sleep schedule as it stands now would probably be 2 or 3 am to 10 or 11 am.
I worked as a RN for years and had to be at work at 5AM. (by choice) I loved getting off at 2 every day. So up at 4AM for me. since I have retired, still the same. People say I am crazy but especially in the summer it is so quite and peaceful, I absolutely love my mornings and my coffee. I always read for an hour. I have extensive gardens and flower beds, so weeding and caring for them in the cool of the morning is nice. i can't stand too much heat, it takes away all my ambition. I feel energized and can get a lot of work done in the mornings. The downside is I am always in bed by 9 o'clock. Many times 8 in the winter. But it suits my inner clock!