Okay, I've decided to throw in my perspective on the topic.
I've had the luxury of playing probably one of the most expensive flutes in the world excluding Powell 365 and Louis Lot 1375 (look these two flutes up if you don't believe me). It was an Albert Cooper Platinum flute owned by a Swedish soloist, Cooper made 94 flutes and this guy owned one of the two (I believe) platinum flutes by Cooper, a silver flute by Cooper, the only nickel-silver flute by Cooper, and the only two piccolos (keyed to low C) by cooper. This was fairly early in my flute playing days and really couldn't appreciate it for what it was, but it was CLOSED HOLE!
Now that I've settled that, the question is what is the purpose of open tone holes? Nobody has really seemed to address that idea.
In the early 18th century, flute makers started experimenting with making finger holes larger, thus giving the flute more volume. This was made famous by British soloist Charles Nicholson (who later influenced Theobald Boehm). Now the problem you might imagine with this trend is that peoples hards are only so big and only people with extremely large and dexterous hands can play flutes with large finger holes. Now queue entrance of Theobald Boehm.
After being impressed with the sound of Mr Nicholson, Boehm set out to make flutes with larger (and more evenly spaced) tone holes. His first system looked similar to that of a clarinet with ring system key closures that were still covered by the finger tips. After some success with this key system he continued his work. He also abandoned the conical bore and adopted a parabolically shaped headjoint bore, but that a lesson for a different time. He concluded that for optimum tone he needed tone holes larger than those capable of being covered by fingers, so he designed the modern flute, which has remained fundamental uncharged since being introduced by Boehm in 1847.
The new flute was licensed to Rundall & Rose in London and Godfroy and Lot in Paris. The French school adopted (have you guessed?) French flutes! Ah yes, to the open hole flute. It's the French's fault, the flute was modified by Godfroy & Lot to have even open holes, giving it yes more resonance.
Okay, so we've gotten that far. Why do we play (or don't play) open holed flutes? The are slightly more resonant than their closed hole brethren. Does that make the flute better? No, not really. Why do we play inline G keys? Because somebody along the way decided that it looks good and we've never been able to rid ourself of that stigma.
Can anybody answer the question of Open vs. Closed holes for you? Not really, it's a personal thing. I doubt most conservatory flutist can really push the envelope between open and closed holes, let alone most doublers. If you can get a good sound on a closed hole flute, why change? While open holes are touted as 'professional', that's a complete load of crap (see Albert Cooper flute analogy above). Although I would HIGHLY advise against getting an open hole flute and closing the holes. Flute companies actually tune the flute different for open and closed hole models. Yes, that's right, change the placement of the tone holes!
Okay, now you know why there are open tone holes so you can make an informed decision. But if you want my 2-cents, the best way to help you playing is to slap a GOOD headjoint on whatever flute you've got (I play a lovely little silver number by David Williams with a 14k riser) on a Sankyo Artist flute (by the way, it is open hole AND inline). This is the most efficient way to get a good sound from you flute with having to sell a kidney.
That's all for now, folks. Hope you took something from this little history lesson. Have fun playing!