In my opinion: Not yet.
Why? Because it won't be worthy for you unless:
1. You're already a lifetime platinum member or you don't care about your membership status.
2. The two programs have already completely merged and Starwood nights are considered the same as Marriott nights.
3. You have no choice (For example: There's no Marriott hotel in your destination).
So let's clarify the above:
Assuming you're not yet a lifetime platinum and you do care about your status (clause 1), and that you do have a choice (clause 3), than our current problem is clause number 2:
These two membership programs are still separated and the only common item shared between them is the points. Nights accumulation is still separated, and you don't get night credits for one program if you choose to use the other!
Therefore, as a Marriott member, if you're not in a lifetime platinum status and didn't get that 'peace of mind' yet, than you should keep making all efforts to achieve this status.
One example (out of many): let's say you want to extend your gold\platinum status for next year and so far you accumulated about 10-15 nights less than the requirement. Will it make sense not to book a Marriott hotel for your Christmas holiday? Of course not! Why would you want to loose the chance of achieving the required 50 (gold)\75 (platinum) nights this year?...