for me that is same. Not worth to buy wt when you have space for mag res. if you organize island good you will have a lot space for mag res to have a lot population from them. of course on some space where is not possible to put mag res worth to put wt. of course you will not leave that space free. for that space wt is better .
i can't write anything in one sentence? every my word i must explain?
EDIT: frozen is even more better than wt (i wrote this for any case)