Differences between coffee made with french press or espresso machine?
To answer the second part of your question ('the pros and cons of an espressomachine'):

Pros:
 - Taste. If done right, you will capture much more of the coffeebean in your cup.
 - Milk foaming. Most espresso machines have the possibility to froth milk for cappuccinos or lattes. Look up 'latte art' on Google Images for some inspiration :-)
 - Process. The making of coffee becomes an enjoyable ritual with shiny machines, hot water and steam.
 - hobby: there is an enormous amount of ustensils, tools, cups, coffees, online forums etc. to discover for enhancing your espresso.  

Cons:
 - Taste! as much more taste ends up in your espresso cup, you will also taste the defects much better (bad or stale coffee, badly grind, wrong water temperature etc.) will give you a sour or bitter cup.
 - Technique. It takes practice to prepare a good espresso (except if you opt for a machine that takes coffee pads - but your choice of coffees will be limited and often not fresh).
 - Cost. Espresso machines (good ones) are costly. And it doesn't stop there. To make really tasty espresso you might want to grind the beans yourself, so you'll need a grinder that can grind fine enough for espresso. After that you might start to suffer from upgraditis...
 - Room on the kitchencounter. An espresso machine can take up quite some space.

Hope this helps!