I think the town should give money to the summer music festival. I believe more people will come to this festival than the winter carnival.
In July the weather is warm and nice, so people like to be outside. Families can sit on the grass by the river and listen the music together. In February it is too cold, many people don't want to go out, especially old people and small children. Also the weather in winter is not sure, if it is too warm the ice sculptures will melt.
The music festival is also good for the local bands. In our town there are many young musician but they don't have many chance to play in front of big audience. This festival can help them to be more famous. Also the bands from other cities will bring tourist to our town and they will spend money in restaurants and hotels.
The winter carnival sounds fun, but I think it is more risk. So my vote is for the summer music festival.