Ive seen this question asked among quite alot of folks so I'll tell what i tell my students as well. First of all lets look at the main differences.
1. Duration :- MSc is a 2 year course , MCA is a 3 year course.
2. Syllabus :- Well you don't have to be a rocket scientist to deduce that MCA has more subjects.
3. Intended Audience :- Most Universities require that MCA students either be a grad in Computer Science or mathematics. I don't believe there is a background check for MSc IT or at least not as restrictive as above.
4. Depth :- Most subjects are usually more in depth than those for MSc. IT students. However MCA programs tend to give you the additive burden of extra papers which won't usually be useful to a fresher in the field but are always good to know. An example, I have a paper called "Software Project Management". I have 3 books for this dreaded subject and its all about maintaining/running Projects in an organization. The chances of you getting a post for project management is near to nil and its nothing you can't understand if you read it yourself or after a few years of experience.
5 Job Options :- I tend to have a belief that there are quite more Job options out there for MCA's (Minimum requirements) but I see that trend changing now.
Of course these may vary from University to University so you might want to compare the syllabi's of both before taking the leap.
Now to the certifications part. I always freak out when I see people taking every other certification in their sight. Example look at this . (No offense meant to Pathik of course)
Do your MCA. AND get yourself some certifications like MCP, MCSE, CCNA, SCJP or whatever.
I think what he meant you should take whatever certifications which would enhance your interest in a certain field. Do not take every single one out there people. Rather focus on one branch on specialize in it. In time you could take others if you are interested.
MCP , MCSE -> System Administration
CCNA -> First step on to Cisco Certifications like CCIE etc. Mainly network configurations and design.
SCJP -> Programming
Instead of taking all the above I would have either gone for a MCP, MCSE, RHCE etc or CCNA, CCNP , CCIE. Anyway I believe that everyone understands my point.
Theres an excellent post by Steve Yegge on the Internet about how to get your resume updated and stuff. I recommend it as a read before you even start writing your resume. Some points are kind of extreme so use what you feel is good or whatever. Here is the link
This is only advice I feel is appropriate. I'm no expert of the field so if you feel I was wrong then just disregard the above.