Zip vs Yellow Letters

[Darrell Lee]

I'm running a campaign for 100% Equity Owners and I have about 400 properties. I'm deciding if I want to run with Yellow Letters or Zip Letters. 

Does anyone have any stories, tips, advice and/or experiences on which has been more productive for them? My first 100 letters (doing them in waves as that is what my capacity can handle) I did through Printing letters via Word and stuffing envelopes. 

Now after adding the cost I'd be much better off outsourcing my mailings.  I just want the most bang for my buck. Marketing budget is only $250 a month. 

Please... All feedback is appreciated.