I'll start this off and then leave plenty of space for more input from others. I have no experience with veilds, but you would rather go with a oustaleti before a melleri, for serveral reasons becaue of cham type, its environmental needs, cb or wc, and your experience.
Another problem is that your helping perpetuate the wc problem when several of us are trying to get breeding programs for this species established so we can displace some of the imports and provide cb animals in the trade. Melleri are less able to adjust to the abduction and confinement of being wc. Also bad for you, because you may lose the animal and be discouraged.
Both are excellent species to work with but if they are wild caught adults, you are going to have trouble with providing conditions that they can adjust well to, getting a suppliment regime for your gutloaded feeders and adjusting them to being handled. Oustaleti is the better choice.
I would recommend you get a juvie panther. There are plenty of resources out there, esp the web. The problems that could arise with raising from a juvie stage are more developmentally based, usually due to diet and suppliments, but there should be less problems with an animal's psycology. If they grow with you they are more likely to be more easly handled, less stressed to confinement, parasites, etc...
Michael