This is the big dilemma that many soapmakers have to face when starting to make soap. Go for the cheap, inexhaustible synthetic fragrance oils (FOs), which can have any smell you like and cost 1/2 or even 1/10 of their natural counterpart, or stick to the more natural but sometimes unbelievably costly essential oils (EOs)?
I have to say I haven't found an answer to the riddle. Pros of EOs are, of course, their very natural and delicious smells, the beneficial proprieties they carry (which are the proprieties of the plants they are extracted from), that can be passed on to the soap, as well as the fact that they make a all around, 100% natural soap. Cons are of course the difficulty to find some rare, expensive scents, the sometimes unbelievably high price and the the fact that you surely have less choice compared to FOs.
On the other hand, pros of FOs are the opposite: you have a potentially infinite choice of smells and blends, you can find anything you want, from green apple to black pepper, and they all have the same, generally low price. But on the other hand, sometimes there could be incompatibilities with the skin, since many of these FOs aren't made for the skin. Plus some of them could make the soap seize in the pot, and what's most important they don't give to soap that nice, natural smell that only EOs can have. Plus they don't carry any property, and they make your soap a little less natural.
Of course, I would rather use 100% only EOs, but since I'm no billionaire, and soapmaking for me is just a hobby and not a business, so far I've stuck to a simple rule: I use EOs for the fragrances that are cheap enough not to make me want to cry when I buy them (these include lavender, eucalyptus, lemon, tea tree, rosemary, ylang-ylang, sage, pine, mint etc.), and FOs for the rest, especially for sweet or flowery smells, whose EOs can cost up to 30-40€ for 10ml!! So I've made soaps that smell like vanilla, rose or jasmine, which unfortunately all contain FOs. Plus I've decided I'll keep looking on the internet until I find a good, inexpensive EOs retailer where to buy my EOs... and if I do find it, maybe I'll be able to stick to EOs only.
In the meanwhile, the refreshing Aloe Vera, eucalyptus and mint soap I'm making is almost ready, so I'd better go and check on it!