During undergrad, students can face several opportunities, ranging from participation in (1) research groups, (2) study/training for competitions, (3) internships, (4) opening start-ups with colleagues (the latter is becoming very common these days), but I wonder, what is really important, for a Ph.D. application/admission...
By competition I mean ones like: INTEL GLOBAL CHALLENGE (VC), ACM ICPC, IMAGINE CUP (examples from the Comp. Sci. field, and Business, but indeed there may be a bunch of these in other fields, that I don't know)
Talking about (1) and (2) aforementioned...
If a student stays a long time during his/her undergrad in a (world-class) research group, he/she is likely to have the opportunity to publish a bunch of papers (some of these might be good, well-referenced, etc; some of these might be not as good), and meet some good researchers around the world, and so on; it really required dedication.
On the other hand, take part into a training class for competitions (that requires dedication, as well) may lead students to gains in terms of working in group, time-boxed activities, etc, as well as to face the opportunity of proposing solutions for real-world problems, and so on.
It is really tough to do both, in order to have great results, since in both cases time and dedication is mandatory. Indeed, there are some "outliers" students that can do both in a very good way, but I'm trying to generalize my assumption, by considering "average" students.
Hence, it's known that good papers have a great influence on the Ph.D. admission (despite of other well-known recommendations, e.g., a great GRE, good recom. letters, and so on), but I'd like to know if (and how) the universities consider students who dedicated their time to join this kind of competitions, obtaining some prizes, as a consequence, etc.
I have found that yes, some competitions do enhance a PhD application. An example is a seminar series competition run by my university that I participated in, we had to speak about our current research (mine was the MSc at the time). I came second and it went in my favour for the subsequent PhD application.