Leaving aside the obvious point that water based oils are widely available under the label 'acrylic' how do true water based oils compare to the real thing, and more importantly are they a true subsitute for traditional oils? The case for water based oils is simple, they are water soluble and therefore don't require the use of solvents, therefore the most important consideration for would be users, is how great is this 'no solvent' advantage compared to their shortcomings. Before we disregard solvents as smelly and toxic, it is worth bearing in mind that while genuine turpentine is both of these , milder solvents such as White Spirit or Odour Free Mineral Spirit (OMS, Sansodor, Gamsol), vary from unpleasant to almost odourless. This is important because solvent has a large role to play in controlling the rheology and drying rate of oils, take this away, and one looses much of the control over oil medium. In terms of traditional oils, solvents play an important part in the composition of oil Mediums. A Medium is not simply a dilutant, but a means of controlling the drying rate, finish, feel, length (rheology) and opacity of the paint. The fact is that water based mediums (or modifiers if you like) with these properties do not exist for water based oil systems - effectively ruling them out for traditional, professional use. So while water based oils have no place in a traditional studio, are they any good for more casual use? Used simply for rapid wet on wet (or Direct) painting there is no reason not to use them but this; painting improves from cumulative experience, practice and understanding the potential of ones materials. Water based oils simply don't have the range of colours, effects and possibilities of the real thing, so ultimately they will run out of things to teach you very quickly, and what they do teach you won't be very applicable to your future development. If you really can't stand the smell, try traditional oils with OMS, and if that's too much for you my recommendation is that you sink your energies into mastering an aqueous medium such as gouache, watercolour or acrylic.