Looking at Eheim's website they do 2 different sizes of Aquastar - 54 and 96.The 54 is 60 cm long, the 96 is 80 cm long.
They say that the 54 is 54 litres. It does not hold 54 litre of water. I had this tank, I had to close it down when we altered the kitchen and there was no longer any room for it; so I sold it. Empty, it held 50 litres. By the time I had put substrate and decor in, the water was down to just 45 litres.
Unless you can squeeze in an 80 cm tank, I would recommend going for the aquapro. It is the same width but bigger front to back and taller. They say the 60 cm aquapro is an 84 litre tank, but bearing in mind my experience with the aquastar, it will actually hold less than 84 litres.
The choice is up to you and your wallet. Both tanks are the same width, but one will hold ~45 litres of water, the other will hold something like 70 to 75.
As for LED vs fluorescent, again the choice is up to you and your wallet.
LED's last longer while fluorescent tubes should be changed every year as the light output falls.
LEDs are a bit cheaper to run, but the difference is not as great as comparing LEDs to old fashioned light bulbs or even halogen light bulbs.
You can choose a different fluorescent tube quite cheaply if you don't like the one that comes with a tank. Some give an orange light, some give a purple light, some give a white light. The tubes that came with my old Juwel Rio were dirty yellow - it looked as though someone had used the tank as a toilet.
Looking at the Aquapro manual, the LED looks to be a flat strip which fits onto 'profile strips' on the sides of the tank. That, combined with the flat shaped lid, will probably mean that you are tied in to using this LED strip and no other make. If you don't like the colour light it emits, you are stuck with it. 6500 K should be quite a white light. If your house bulbs of whatever type have a K rating on them, see if you have one at 6500 K and decide if you like that colour.
Or go for the fluorescent option, because you can replace them with retrofit LEDs should you later decide to go for LED. That's what I did with my Aquastar
This A shop quite near me sold them, so I looked before I bought. The colour plus turned the tank orange so I got superbright. I also have these tubes on my 180 litre tank.
As for glass thickness, the taller the tank, the thicker the glass needs to be. I had no problems with the Aquastar.