1...e5 vs 1...c5 - against 1.e4

I think 1...e5 is better for people who are lower than 1400

Beginner - I like e4/e5 since it's going to teach the very basics and emphasize tactics more. 
Novice - this is still such a low elo I think I'll stick with e4/e5
Intermediate - At this point I think you're good enough to understand basic concepts like *what is an opening*, *should I respond to my opponents moves...?*, etc. ... and we shouldn't necessarily treat you like an elementary schooler. You'll acquire tactics as you keep playing and your rating will natural climb. In the mean time you should just start experimenting with the opening. For one, experimentation is an essential phase in opening development, and it takes quite a while to experiment enough to where you know what you want to play... many years. You'll learn alot about the game through the process, every opening will teach you something. But the earlier you settle on which line you want to play... the more years of experience you'll have with it, by the time you reach 1800... if you already have 4 years experience dealing with anti-sicilians, that's a good thing - that's the next 4 years you can spend studying endgames or whatever else. You don't have infinite time so figure out which opening you want to play.

To anyone intermediate and above I'd recommend the sicilian, given that you've experimented with the different options. Except maybe if you're playing the Petrov, that's the only exception. But in e4/e5 lines in general white has the control of the game, and the lines are very tactical... to play this style requires quite alot of memorization, but still there are so many deviations in e4/e5 and when they occur it's usually white entering them, i.e. you're at strategic disadvantage. It's a very rich position but I don't think it favors black.

Sicilian... black has the control in the sense he chooses the mainline variation. You can play the Sicilian in almost any style, and it's' blacks choice which style... There are also more opportunities for black to deviate, even in anti-sicilians. The other nice thing is, since it's more positional, i.e. it's less algorithmic... and combined with its vast size and the fact black has control... it's not as easy for white to rotely memorize everything. Which matters alot, since e4 is the most common move in the game... you don't want something that gets played out quickly.

And another perk is the Sicilian can augment your repertoire against the English and Reti.

Systematically play through the openings. Don't play just one opening. I wish I didn't stick to one type. First, chess is more fun with variety. Second, you learn more with different positions and similar tactical situations. Play a couple in one opening, then play another. Maybe against 1.e4 play e5, then d5 and c5, before cycling through e6, d6 and c6. Against 1.d4 which you still see less at the lower levels try d5, c6 and e6. A nice range of games.

Spogettee and Pork.