Seeing as you're likely to get a bunch of smartass responses, I'll try to be a bit objective here.
I've been on both sides of the fence: a raging stoner, wake-and-bake, don't leave the house without a smoking a bowl, roll a road doobie, long hair bloodshot eye type. I went stone cold sober for about a year, then started smoking again. Still haven't returned to the constant high-tolerance smoking I used to. Different times in life I suppose. Either way, I feel I'm in a position to give a fairly reasonable response. Now, to answer two primary questions in your post:
What are the differences in using these two?
Sativa: racey, energizing, often panic inducing to the uninitiated. Some varieties can even lean towards the psychadelic variety. Great for daytime, social events, creativity, get-up-and-do-shit smoke. Flowers tend to be airy and large.
Indica: sedative, pain relieving, "in-da-couch". Heavy eyes, not so cerebral, lots of body effects. Generally advised for stress, anxiety, pain relief. Good for night time, chilling out, aiding sleep. Flowers tend to be tight and compact.
Which one is better?
This is subjective. Some prefer sativas (Jack Herer snobs, anyone?) and some prefer indicas. Some prefer hybrids (good luck finding a non-hybrid these days). For a first time smoker, I'd recommend a moderate THC level. You're not prepared for the 28%+ types. When states here in the US started to legalize, there was a huge boom in Blue Dream. Shit was everywhere. It's a hybrid, bit more sativa dominant, and decent THC levels. It was "the" entry level strain. All that being said, what's best for Joe is not the best for Susie. You just gotta pick one and run with it.
Now, for the pros:
I've made some of the best friends I've ever had, with our relationship icebreaker having been cannabis. It can improve sex, musical experiences, ease anxieties when dosing hallucinogens, enhance opiates, facilitate relationship building, improve creativity and focus, relieve stress, make parenting easier and more enjoyable, and generate a little revenue if one is so inclined.
The cons:
People become lethargic. Long term, excessive use has been shown to exacerbate symptoms of depression and anxiety. It can result in one being incarcerated in certain parts of the world. There are health impacts associated with smoke inhalation, especially of the organic varieties within organic material such as cannabis. It can induce panic attacks (this is what it does to me now). Due to the lethargy, it can lead to isolation and eventual agoraphobia, leading to further isolation. It is habit forming. One could become associated with a lifestyle or idea of a lifestyle that they are not accustomed to/do not want to be associated with.
At the end of the day it's a decision you have to make for yourself. I'm pro-drug. Try what you will. However, cannabis isn't going to kill you, so if you're curious get some that is moderately potent and give it a go. The worst that will happen is you'll be uncomfortable for a few hours and be done. Then you'll know if it's for you or not. Otherwise, you'll find something that makes you happy and go on with your life. It's just small stuff, don't sweat it.
