Well it used to be that the ore library of resources was greater than the enmatter but recently
MA has introduced more enmatters so I think they are getting closer to being balanced.
Its hard to say just which one to pick and honestly if you are going to be a hard core miner I would say look for both if you have the ped. Ore and enmatter fields seem to overlap so you can maximize returns looking for both just be aware you can loose much more this way too.
Some benefits to enmatter mining: 2 probes for one ped(more chances for skill gain), enmatter amps last longer (well at least the ones I use), there is now a greater variety of enmatters and you can find a great many of them with the right skills and equipment. Since enmatter is not as popular the equipment can be cheaper.
Some draw backs: drilling is slower than excavating, enmatters tend to have a low %, unless the rig is still broken, oil can be gathered from the rig which does tend to impact the price of probably on of the first enmatters you will find.
Its a tough choice and I guess thats why I choose to look for ore and enmatter its not always a sucessful venture but it does raise those skills and helps you learn the resource markets from both enmatter and ore perspectives.
Maybe trying both at seperate times will give you a little more insight and help you make a decision on one or the other or both.
Good luck and happy detecting.
