Washes: Oil or acrylics?

Like you, I have been using acrylics for the washes.  I have used oils for washes as well as detailing and painting whole sections of models.  I painted the exhaust on my 1/72nd scale X-32with oils, and frankly it has one of the most realistic finishes in my collection.  The down side with working with artist oils is that they can take days, sometimes weeks to fully cure.  this can be solved by adding a quick-drying medium called Liquin, available from Winsor & Newton.  This speeds the drying comparable to such enamels like Model Master, Humbrol, etc..  I also incorporate the use of a home-made drying oven to help speed drying.  Also, I have experimented using alkyd oil colors, rather than standard artist oils.  Alkyd colors simply dry faster because they are formulated with a modified alkyd resin in the paint.  When I want speed, I'll reach for the acrylics, but I sometimes go for my oils for that special touch only oils can provide.  For oil washes I thin them with Testors brush Cleaner #1156.  The brush cleaner is not as strong of a solvent as the airbrush thinner or enamel thinners.  A word of caution; airbrush thinner can disolve an underlying Furture coat, running the risk of damaging the subsequent color layers.  I found this out years ago the hard way on a contest model!  Another good thinner for artists oils is Turpenoid.  It is the standard artist quality thinner for these paints and is gentle enough not to harm the underlying finishes.  So give oils a shot and report back here with your results!  hope this is helpful.  

I've used both as well and to be honest oils look better to me... but as mentioned are a bit more work to put on.  I tend to use acrylics more on the interior of my planes and a bit more with oils on the exterior as they are more visible there...

The part I like about oils is they are workable for a longer period and once the thinner evaporates, you're not relegated just to getting the part of the wash you dont want off, but more to spreading them to the areas that you need it...  more forgiving but as mentioned it takes a few days to dry...