lol VU, heard of, but don't know anyone's who's done it.
1. Do the offered subjects interest you? Honestly think you should only do extension if you care about the subject, not just for getting the 5/5.5. But yeah, if it doesn't interest you, you'll struggle to cope with learning new material/attending classes which subsequently might cause you to get 0 or scrape a 4 (It's not even that hard to get a 5.0 at Monash to be honest, you just need distinction average). You'll also be intensely disatisfied/distressed if you hate it and this mood might affect studying for your other subjects.
2. Location - would you be able to access the teaching place? How far/how much time wasted/will you be too tired?
3. Quality of the program and facilities offered. *I shall refrain from Group of 8 snobbery and stereotypical comments about drug dealers that may offend people*
4. Credit - you probably won't get credit at Monash or Melbourne for VU extension subjects, since they don't usually see VU as an equivalent.
Not as difficult = not as intellectually stimulating = defeats the purpose of the program.