1. Waterfall Model the tester role will take place only in the test phase but in V-Model role will take place in the requirement phase itself
2.Waterfall madel is a fixed process u can't make any changes in the requirement or in any phase.but in V-Model u can make any changes in the requirements
3.V-model is the simultaneous process but it is not in case of water fall model4.waterfall model used only the requirements are fixed but V-model can be used for the any type of requirement(Uncertain requirement)
In this model if one stage is completed then only will go to the next. So Testing will come after development of entire system or application. So due to this if any change request/requirement comes in between any stage then it will be very tedious since agin starts with the first one. So it is very time consuming and costly.
This is same like "Waterfall model" but in this model "Testing" will come and each and every stage so that in earlier stage itself we can find out any flaws or if any changes comes in any stage we will rectify immediately. So it is very cost effective.
I think i haven given mostly correct answer. if any changes guys let me know.