Either could work. Some people run tanks with large fish like that with JUST sponge filters and nothing else. It's all up to what you think looks best really.
They're both really cheap to buy. Box filters can look a bit ugly, and have more customization options than a sponge. Sponges look a bit less ugly especially against a black background. Of course they can't really be customized, but they do provide a higher mechanical filtration than the boxes. Although some people say their larger cichlids tend to tear them up a bit with biting.
I'd run a combo of both honestly. 3-4 medium/large sponges and 2 nicely sized boxes. All should cost a lot less than a HOB.