I've been using the HOB for about two years now. Inside the tank, it doesn't take up any more room than a drilled overflow would. Mine is a single drain pipe because it's just a 75 gallon but yours would obviously be at least two drain pipes so there's more security/redundancy there in terms of clogs, but I've never had one.
48" light sounds good but it very much depends on the type and quality of the diodes. A 48" Current USA bar is nowhere near as effective as even a regular black box LED, depending on what you're trying to grow. With your setup, I'd heavily consider at least supplementing some T5 with whatever LED's you choose to go with.
Here's my two black boxes on my 4' tank. You would easily mount them into your hood.