the biggest problem with undergravel filters is that because there are no moving parts, people often assume it's a "set it & forget it" thing. UG filters require as much regular maintenance as any other type. Using a gravel vac every water change and routinely siphoning from under the plates go a long way to preventing the compacting issues and muck build-up.
Now undergravel filters and canister filters are NOT nitrate factories as is often mentioned.
The fish, other livestock and the bacteria are the nitrate factories. The reason certain types have gained that reputation is because they trap lots of detritus and if poor care and maintenance practices are employed, then you have issues.
In actuality undergravel filters are one of the best methods for biological filtration, if properly maintained.
Now having said all that, you will ultimately have better success, especially with a reef tank by not using an UG filter. The reason being is that in order to maintain it properly, you need to disturb the substrate frequently. While that really would present no issues in a fish only set-up, in a reef the micro-flora and fauna that reside in the substrate can be a vital link in the chain of maintaining equilibrium in a reef environment, so the frequent disturbing of the substrate could present issues.
Also in a reef tank we tend to setup the rockwork, coral grows and the rock is pretty much set in place. That is a problem because it precludes vaccing the entire gravel bed.
So undergravel filters are great in certain applications, but in a reef tank they can present more obstacles than solutions.
My best personal success with UG filters has been smaller freshwater, planted tanks.
I did have one on my reef tank at first, but ditched it when I upgraded for the reasons I cited above.
Hope that answers your question more fully.
