I'm beginner chess player who like aggressive play. I often counter e4 with e6(french defence) or c5 (sicilian defence). But I still don't know what's detail pros and cons with these openings. Can anyone explain me? Thank you very much for your answer. I appreciate that
The French and the Sicilian are almost as different openings as you could get as a response to 1. e4. The French (especially the Advance Variation, which is the most common among amateur play) tends to lead to closed positions, that is, positions clogged up with stable pawn chains where long-term maneuvering and strategy prevail. The Sicilian (as much as there is a "single" Sicilian, seeing as the multitudinous Sicilian systems can range from quiet and defensive [cf. the Sheveningen] to dangerous and aggressive [cf. the Dragon Variation, or the Sveshnikov]) tends to lead to open or semi-open positions, and the tide of play may shift within just a couple of moves owing to tactics.
There's really not much to be said in terms of meaningful, general, and objective "pros" and "cons" of the two opening systems. I would just study very briefly the theory behind the first few moves of each, play several games with them, and decide for yourself which you like to play. They're both super-solid in principle and played all the way up to the GM level.
(If you say you like aggressive play, I tend to think you'd like the Sicilian as such. The French is still among my favorites, however, because as Black you're constantly making White react to your threats of winning small but significant positional or material gains whilst in the opening. As a beginner I found games almost played themselves and if White wasn't keen on defense I would obtain the upper hand.)
Each opening is good for trying to introduce potential imbalances. The Sicilian is very popular, and you may have to learn a few opening lines, but don't memorize too much. You'll recognize move-groups or ideas or piece formations that work. Playing ...d5 is generally the goal.
The only drawback is that White can often have a general plan against any sicilian e.g. f4 O-O with a kingside attack, or a quick g4-h4-(g5/h5) with O-O-O. You need a certain degree of confidence against both.
The French Defense often leaves you with a space disadvantage and a bad queen's bishop, since White often plays e5. Black's moves also feel relatively logical if you look at a few GM games. And "just developing" often gets White's position in hot water if he doesn't understand his weaknesses.
I learned a lot about pawn chains and such from playing the French Advance: e4 e6 d4 d5 e5 c5 and Black can do a lot on the Queenside. It's also relatively harder for White to sacrifice soundly against the French. The Milner-Barry is about all there is, though the Alekhine-Chatard can be a pain if you play e4 e6 d4 d5 Nc3 Nf6 Bg5 Be7 e5 Nfd7... h4!? burned me.
But the big drawback of the French is e4 e6 d4 d5 exd5 exd5, the exchange, which is potentially boring, and lower rated players may use it to try to draw against you and frustrate you.
I played the French when I was younger. Sometimes I wondered if I should've gone with the Sicilian. There's no wrong answer.