Interior Casing: Poplar -vs- MDF

Carpentry newbie attempting to build a 3 piece victorian window and door casing. For a painted casing, which material MDF or Poplar is better and why? (Can I get away with using the less expensive MDF?) FYI: I may be routing an Ogee detail into the material if that makes any difference.
Thanks.

 

hi
mdf is fine
check there some premade mdf moulding
you might used

 

I've been using MDF for a while now, i made the switch because my paslode finish nailer would split the casing sometimes and the MDF is kinda bendy.Wood gets warped real easy laying around so MDF works out just fine.

 

The only problem with MDF is that it CANNOT get wet. If the windows would ever get left open during a rain, it would probably cause the MDF to start to swell. You see this a lot with MDF casing where a fire sprinkler system went off, the casing is malformed where it sat against the wet carpet too long.

I frequently have to use a mixture of MDF and poplar on painted window trim jobs. There are certain moldings that I won't make out of MDF. MDF paints well, but requires a heavy coat of primer, then a light sanding before painting. Poplar also paints well, but may require a little more sanding after it is primed, due to the wood fibers raising.