If you ask this question to ten people, everyone will give you a different answer. So ultimate choice is with you. You can't say this choice (writing 1 group) is good or the other is bad (writing both groups) because all choice will have their own pros and cons, like for e.g. set off between groups when writing both groups, rank when writing both groups, limited time when writing both groups. You can get rank only if you clear both groups together.
However, since you have sought opinion I will give you mine:
Concentrate and clear Group I, so that you can start your articleship and your final attempt is not delayed. Many students feel Group II of IPCC requires just half the effort you require to clear Group I. So you can clear it once your articleship starts.
But as I said, ultimate choice is with you. The above opinion is just my take on the situation. You may however write both groups and get a rank too.