If you are set on an etek3, then go for it. However, there are many other options out there.
First, you are asking the difference between an etek3 and a reflex. Well, they are two completely different guns. The etek3 is a poppit, the reflex is a spool valve (note: the reflex is not the same bolt as an ion. Every spool valve is based off of the same design.)
You should look into the difference between a spool and a poppit before you decide. There are pros and cons to each. A poppit will be more efficient on air, requires less tlc, will have more kick, and are louder. A spool will be smoother, use a little more air, and will require you to lube it after every use and check orings more often.
If you are looking into new guns that would be good starting tournament, the Reflex is a good choice if you want a spool. For the poppits, the etek3 is good, as is the Empire Axe.
However, used isn't a bad way to go. Before you buy used, you can view a person's feedback to see if they have sold high-end markers in the past. You can also make a Want To Buy (WTB) thread in the appropriate forum of the Buy, Sell, Trade (BST) section where you can post what you are looking for and people will bring you offers. You can pick which ones you are interested in and work a deal out with the seller. For used guns, you can get many different guns that will perform all around better than an etek3, Reflex, or Axe will and you can find them for the same price.
Here are some used used guins you can look for and some of the prices I have found them for:
Ego 2007 : 350-400 (poppit)
Ego 2008: 375-475
Ego 2009: 475-550
Ego 2010: 550-700
Geo : 450-650 (depends on if it has Gst kit and Gr2 bolt) (spool)
Creed: 450-600 (poppit)
These are either love them or hate them markers. It all depends on what you like. Here on pbn, you will get people that completely love the creed and swear that is the best poppit out there and you will get people that say they hate it. It is different from most poppits in that the LPR and HPR are balanced and you use the LPR to adjsut your velocity rather than the HPR. Be sure to read how to adjust and tune a creed before using one. If you know how to work it properly, it will be one of the best shooting guns you can find on the market.
Dm 2006 : 250 -350 (spool)
Dm 2007 : 350-450
Dm 2008 : 400-500
Dm 2009 : 475-550
NT 10 : 550-700 (more efficient than a Dm, but less reliable)
Intimidator: 200-650 (poppit) These are good guns and can be found for a very good price. I would suggest looking into getting a G6R. They can be found for 650 and will easily compete in any paintball scenario.
Marqs : 250-800 Same as the G6R. The marq victory is a great gun. They can be a little pricy, but an older marq rapper or closer shoots just as well and can be found for under 400. Bob long guns are virtually indestructable.
DLX Luxe (spool) : 650- 850
Smart parts Shocker: 150-350 (spool)
Smart parts went out of business a cople years back, but their shocker marker is a great gun and there are plenty available for cheap. Plus, GOG will service any smart parts gun. For the money, look into a shocker NXT, possibly a private label one.
Again, do some research, see if you can try some guns out at your local field, look around the companies forums, and find a gun that is right for you. Don't base what you are going to buy off what someone thinks is the coolest new gun.
If you have any questions about markers, their pros and cons, how they perform, upgrades available, etc., drop me a private message and I will do what I can to find the gun that is best for you.
ps. you wanted an essay.