I haven't tried many apps - I get hints from reviews and notices, and have three which I use for various reasons. I would note I am not a power user - don't share calendars, invite people or use a number of different ones. They are for me!
Itunes web link
This was the first calendar I got and I still use it. As an academic, during semester time week view is my main visual handle on my timetable - it changes from week to week and a good visualisation is essential. Week Cal's raison d'être is the week view (day and month views are available). Entering new events is straightforward using the normal touchdate/time, make selection about length from the tumbler etc. All the usual features expected of a calendar are there too - location, link to contacts, repeat, different calendars.
I was happy with it, but then read some reviews of other with different tweaks, and I now use 2 of them.
Itunes web link
The first thing is that this integrates calendar and reminders, so it is a nice integration, especially if you keep trying to get todo lists - at least they are together here.
Second, it uses 'natural language' item creation. Tap the + button and you get a text entry line and as you type it in the program makes its interpretations - meet student at 2 will start to create a meeting at 2 today, add tomorrow and it will shift the draft to tomorrow. Start the typing a todo and it will be a reminder (there is also a sliding button which will toggle between appointment and reminder. If it looks OK hit add, if not you can look at the details and fine tune it and add the regular stuff.
The next difference is the look. When you open it you get a ticker tape of days across the top (not showing sequences of more than 3 days without a meeting) with bars representing meetings for the day. Below is the current reminders and then a list of meetings.(Tap for more detail). As you scroll the list, the ticker tape slides across.
Drag down on the ticker tape and it changes into the month view with dots for meetings and also a search function.
I would use this as my main calendar except that the week view is available only when you rotate from portrait to landscape. As my phone is locked in portrait, that is a nuisance and effectively no use (one cal app I looked at had a button that shifted the view from day to week - much better - but it didn't add a lot more.
At the moment I am using all three because they have different advantages and fun (Peek) and would only go down to 2 when Fantastical can replace Week Cal.