If my math is right, the tank is 20x32x18, right? You're in a really good spot there to pick the kind of lighting you want. I'm personally a fan of LEDs because they are lower power, produce less heat and don't require you to change bulbs (ever in theory). That said, T5s have a lot more experience under their belt and they have been more refined to our hobby's needs. You could buy a T5 setup and a typical assortment of bulbs and have great success. With LEDs, there can be some nuances to consider. The ease with which you can adjust some LED setups means some people mess with them too much and wind up having trouble.
There are inexpensive versions of T5 and LED fixtures out there which would suit your needs.
For LEDs:
You can get two AI Prime HD LEDs and I think you would be extremely happy with the results. They are $225 each, plus mounting arms or you can hang them. You can control them from your phone so no need for extra equipment. You could also go the DIY route with something from RapidLED or any of the others out there. This let's you customize for around $300. Or you can go with the so called "black box" LEDs. There are some reputable names there now, like Ocean Revive's T247 fixtures. They're fairly inexpensive too. I run a Kessil A360 over my 50g cube and love it. You'd need two for your tank dimensions though due to the width. You could also go with two A180s.
For T5:
The prices range from $50 for a really basic fixture (plus the cost of bulbs) up to around $1000 for the size you'd need. Bulbs need to be replaced every 6-12 months, depending on who you ask. Prices for bulbs would be in the $50-100 range each time.