Being the proud owner of products from both manufacturers, I thought it appropriate to compare/contrast a much under appreciated tool from each company - the measuring tape!
Both are high quality befitting such companies and both have their pro's and con's, to wit:
Size. The Felder tape fits well in my hand. I has a handy carry strap but I don't know anyone who would be girlie enough to use it. The Felder is 16' long and the Festool is 10'. The Felder tape is a bit wider too so it holds it shape a little longer before breaking over.
The markings are comparable but the Festool is both Imperial and Metric and the Felder is only Imperial. However, with my old eyes, it's hard to see the metric markings clearly without reading glasses. However, the Festool has this handy window on the top to view the markings. Very clever.
The Felder has a dual blade locking system. The traditional slide on the front of the case which will hold the blade hands free and another one at the bottom which is used to hold the tape only as long as the user has the button depressed. The Festool only has the traditional locking tab.
The Festool has this circle drawing attachment at the bottom with a point on the end to use as a pivot. There is a small hole at the one inch mark so you can put a sharp pencil through it and then arc around the pivot point. The Felder has the same hole at the same spot but no pivot point. I suppose it would be useful to scribe a line while using your thumb and finger against the edge of a board but drawing a circle would be problematic.
The Felder also has a belt clip and the Festool doesn't have any way of attaching itself. You have either put it down somewhere or in your pants pocket. Not the best idea.
All in all, they both work well with each brand having their own unique features. I usually choose which ever one is handy.