I would just ask you to consider a case (if its possible to have both function together.)
We have large files. 1500 rows by many columns depending on area eg:
Base information is in column 1 (so the 1500 rows are relevant to each area.
The following data belonging to different areas is in the rest of the columns - in some cases 40 or so columns.
Ie area 10 matches row 100 - 600 etc.
The Responsive extension works however for us the issue is the required data to match the area to (ie column 1) moves off the page as they scroll through making the column data in say column 10 and further have nothing to match to..
If we only have fixed column, the grid larger than the site page etc..
Hope that makes sense..