Both Idea Likes (ballot icon) and the Star Rating provide useful information throughout challenges. Both methods are quantifiable. Each has their advantages. A simple binary idea like is much quicker for a user to perform than choosing between the various number of stars to assign an idea. Star rating is more granular: you can measure the degree to which a voter likes an idea. The attached Voting Dynamics White Paper provides extensive background into and comparison between the two systems. Below is an excerpt, to give you an idea of the advantages of both methods. Note that Planview Spigit has a "like" vote that resembles a ballot box and is equivalent to the former Thumbs Up vote. The thumbs down feature was deprecated for reasons detailed in the article Idea and Comment Voting.
Only Up Voting (to respect cultural norms yet still enable)
One way to address the cognitive and scaling challenge of distributed attention that occurs as the volume of ideas grows, is to simplify the voting even further – by only allowing a "like" or up vote. You’ll recognize this model from Facebook®. Indeed we know that in the social enterprise setting, down voting is not particularly heavily used even when enabled. We also know that down voting is considered culturally inappropriate in various global contexts. We find a 6:1 ratio of up to down votes on average in the innovation context. Thus it is a natural option for such contexts to allow only up voting. However, while this model may match more closely the cultural norms of the enterprise, and it slightly lightens the cognitive load for the user, in essence the scaling difficulties remain as the pool of ideas gets large - one’s attention still tends to be divided across that pool of ideas, and is typically still focused on only a few.
Star Ratings (to elicit the voting granularity needed for the decision-making context at hand)
For situations that require more granular voting feedback than the up/down provides, a star rating or other rating scale is appropriate. Star ratings encourage people to think more carefully about their choice, and provide a finer-grained opinion (bad, okay, good, very good, excellent, for instance). Places where you have likely seen star ratings are on Amazon® and IMDb.com. With star ratings, one of the key challenges is making clear what the rating scale signifies - so that there is consistency in the interpretation that leads to an accurate aggregate view. Star ratings also suffer from the challenge of distribution of attention as with up/down votes.