Polartwins,
There is a lot of good advice passed along on this topic. Yes, a lot of them contradict each other but they are all opinions and as the saying goes everyone has one.
Instead of trying to give you my opinion (which would take hours) I will try to stick with facts (but opinion will surely slip in) so you at least have a basis for a decision.
Quick background on myself so you can see where I am coming from. I enlisted in the Army as an avionics tech, got accepted to WOFT as an E-3, and flew Apaches for six years before getting out of the Army (just under 10 years total). After two years of being out I became a commissioned officer in the Coast Guard and have been in about 6 years now and planning to stay until they kick me out. So I didn't go through the high school to flight school way but I didn't have any college when I went either. I was 19 when I started flight school.
Now to your questions. The difference between a warrant officer and a commissioned officer at the unit level is very negligible. Outside the unit is where the big differences come into play. At the unit a WO-1 and an O-1/O-2 have about the same experience and will be learning the aircraft and the mission. The WO-1 will be able to learn the mission and perform flying duties without too many outside distractors except for a small additional duty or two he must perform for the unit. The O-1 will be learning the mission and flying but will also be the Platoon Leader trying to learn to be a leader and be in charge of around 15-20 men. Both will be on the same missions and both will be expected to progress in their aircraft.
So they are both learning with one having more of a burden placed on his additional duties. But that O-1 will only be doing the same thing for a couple of years. After that, or even before he got there, he will be spending time as a staff officer. He won't fly much at all in these positions as flying becomes a secondary duty to the staff position he is holding. Commissioned officers must bounce back and forth between being a line pilot and a staff officer for their first 6-8 years. After that they will be lucky to see a cockpit again for any amount of time. Meanwhile a warrant officer, with some exceptions, will not have to leave the line unit his entire career.
Both have their pros and cons. You will have to decide what you want out of your career. On a side note, commissioned officer pilots in most services are set up more like the warrant officer branch in the Army until we become senior O-4s. I will use myself as an example. As an O-3 I am not in command but I am in charge of a few people. I have additional (collateral) duties that are a little bigger than a warrant officers would be and I must allow time for flying and my duties. But I will fly my entire career with my flight time tapering off a little bit as I progress above the rank of O-4. The only time I won't fly is if I do a tour at headquarters which is usually a couple of years out of the cockpit (I don't plan to go there). We then compete for OPS, XO, and CO positions as we increase pay grades. That is why you have read all of those comments about going into another service if you already have your degree. I will admit that the quality of life is much better where I am now but the grass isn't always greener.
Now for your other question.
You most likely know the prerequisite requirements better than anyone here but if not, try this site:
http://www.usarec.army.mil/hq/warrant/ . You will notice that college and flight training are NOT prerequisites. But if you have them they certainly help. The boards have been odd over the last few years. One time they will barely have enough applicants while others will be well stacked with many qualified applicants. So your odds of getting picked up on any board really depends. Your age doesn't matter, your maturity level does.
Know what you want and go for it. Talk to a recruiter. Despite urban legends, they do get credit for sending in a flight student. The problem is they have to work harder for it. So if you go, help him out the best you can and do what you can on your own. Don't expect him to care as much about your packet as you do.
After reading all of this and no matter what you choose, remember that if you don't submit a packet for consideration your odds of being a military pilot are zero. It is like the lottery, you have to play to win.
. In general as a warrant, you will have a primary responsibility in a technical area. If you are a rlo, you'll find your primary responsibility lies in the leadership role.
