/agree with Mala. Take em all and figure out what you like. If you play a limited amount of time though, definitely be a combat character. Crafting once you start mining your own resources and stuff is VERY time consuming. You end up spending so much time keeping your business running that you have little time for anything else in the game.
With my Master CH/Commando I saw every planet in the galaxy, hunted nearly everything there was to hunt, did theme park missions, etc.
With my Master Artisan/Master Architect/Master Merchant I hardly ever left Naboo and most of my play time was consumed with keeping up with resource shifts, checking harvesters, crafting items and keeping vendors stocked, etc. No time to do anything else. I was so relieved when I finally decided to pop my holochron and it sais "Master Swordsman"! I quickly had a Going Out Of Business sale on my vendors and took up arms! Having a blast as a swordsman.
The end result is the high end combat characters all are good at what they do. The best solo characters (since they nerfed CH's) are probably Bounty Hunter, Commando, Swordsman and TKA. BH have powerful attacks which target the mind pool and can drop powerful mobs (and players) pretty quickly. Commandos with a flamethrower have one of the best DoT's in the game and do massive damage with Area of Effect. Swordsman kind of combine those two, although not ranged they have stackable mind pool dots and big mind targeted attacks which can drop some of the strongest mobs in the game in a single hit and they also have Area of Effect attacks making them one of the strongest solo tanks out there. TKA can dish great damage and fast but they have the limit of one target at a time. Their upside, however, is the meditate line which allows them to heal themselves massively in the field when no medics are around. That is a huge plus for this class as downtime is greatly reduced for them.
Either way, once you find what you like, you will find there are things you can do with whatever your class is that others can't and after the next rebalancing of combat in an upcoming patch you will see all elite combat professions somewhat in line with each other.
Hope this helps.