You are looking at a good sized starter tank there in a 4ft'er, very good choice
External are widely condidered the best filters on the market. On a tank this size, I'd probibly give the internal a miss. They are great for smaller tanks, but just don't cut the mustard when you pass something the size of a standard 3ft...
The UGF (Under Gravel Filter) system is great for Biological and Mechanical filtering, but is limited in it's chemical filtering capacity and is a royal pain in the back end to maintain. Also, they force you to keep the gravel level, or your filter suffers "channeling", where almost all the water flows through the shallowest section of gravel. Finaly, UGF's require a tank strip down every 6 months so you can clean underneath the filter plate...
In your situation, I'd likely look at an external canister filter.
Where abouts are you based? It is useful to know so we can make equipment recomendations, as well as for things like meds (in the hopefully unlikely event you need them) as well as "essentials" like test kits and suppliers of Ammonia for your fishless cycle... This leads nicely to my next "tip"
I'd advise you to sift through the
"beginner resources" section to get up to speed on maintanance, set-up e.t.c. Probibly the two most useful articles in there though are
Miss Wiggle's "setting up a tank" guide, and
RDD's "Fishless cycling" guide, using liquid Ammonia. You can do a fish-in cycle, ut as you will see from reading
my article on it, this method is hard work. It involves adding fish after a few days, but this usually leads to several fish deaths, disease problems and stress. In a tank that size, your upper body strength will improve also, due to lugging large ammounts of water about on a daily bases
Take the easier route, fishless cycle your new tank
All the best
Rabbut
