You do you, but it's better if everyone donates a bit of money to a lot of projects than donating a ton of money to a single project. It's not like a single individual with a normal salary could fund a project alone anyways.

Let's suppose that 10 people have 10 dollars to give each, and there are 4 projects which they all use: Project A is the most important for 7 people, so they recieve $70. Then comes project B with $20 and C with $10. Project D gets no donations.

But if we ponderate them by average importance it would be: A=0.5, B=0.3, C=0.15 and D=0.05. If they had split their donations, the allocation of funding would have been way more efficient.