Purchasing a harness is a big investment. If you think you'll only own one harness consider how much time you'll spend showing versus driving for fun. If you're a serious show person you'll want to have a work harness and one that's just for shows.
Everybody loves a russet colored harness. The main reason they're not more popular is its very hard to maintain that wonderful color if you use it at all. It stains from sweat and needs to be oiled to stay supple. Oil will make it darker too. If you truly love the color consider a biothane harness that won't darken with age. I purchased a black harness with russet trim on the breastcollar, breeching, brow band, and nose band. After using it for a few years the russet was almost black and looked like poorly stained black leather. I went ahead and stained it, added a new brow band made with a bead of gold leather, updated the breastcollar and have a new looking harness!
FYI - If you decide to show in ADS shows remember that your carriage fittings need to match your harness, for example with russet harness the leather on the carriage must be russet also, the running gear (any metal parts that aren't brass or chrome) must be painted dark brown. For ADS even a black harness should have ALL brown reins, not reins that are half black and half brown. *Please remember that these ADS rules are only a matter of a few points. I've won a turnout class with a marathon cart and chrome fittings just because my horse went better than all the others.*
For myself I'm hooked on leather. I love how it feels in my hands and on the horse. I get my harnesses directly from the harness maker so I can ask for any bell or whistle I want. BUT you have to know what you want.
TICA - You asked about using a wrap strap or a buckle down over girth. This can make a BIG difference! If you're only going to drive in a ring and planning to show in breed shows only a wrap strap is what you want. The wrap strap basically ties the shafts to the horse's sides. This can allow the horse to pull the cart with his back and can eliminate the need for a breeching. You can tell the horse is pulling with his back when the traces are flapping loosely.
IF you plan to drive outside a ring, down the road, over hill and dale, PLEASE use a buckle down over girth with an open tug. The horse will be able to pull all the weight of the cart with his chest using the breastcollar. The open tug will allow the shafts to "float" meaning as you go over bumps the shafts will go up and down, not jarring the horse or you. The over girth should never be tighter than the girth or they can rub the horse's belly raw. I hope you can see how the shaft can move in the tug in this picture.
Sorry to go on and on. You can tell I'm passionate about harness!