I am looking for reports/articles/research on how SMEs and big companies differ in their approach for finding and buying IT solutions. I would expect that ROI and the cost of the ownership play bigger role for SME than for bigger companies -- which most offen have more cash and look more for, e.g., easy integration of the new IT solution with their exiting IT landscape.
[ I'm going to answer with the assumption you meant SMB, not SME. ]
Small and medium size businesses (SMB's) tend to be acquiring a product to fix a problem with their business processes since. They are still growing, and the old systems didn't grow with them. On a per customer basis, saving x% per transaction will be difficult to notice, but freeing up 10 hours of an employee's time per week will make a huge difference.
For enterprise businesses, all that money is counted at the end of the quarter and a small difference shows up with happy or upset shareholders. Saving a small % per transaction results in a significant return because of the scale of the company. Reducing the time for employees to perform a task will either be a significant savings spread across the company, or of course it could also mean laying off people that are now redundant. They should already have a well established business process, so you have to show an ROI to prove that your process is better or will save them money somehow.
So to answer your question, I think it's reversed. SMB's care about seeing some kind of benefit from your product, and enterprises care about the ROI.