They wrecked the filter and lighting in the new tank IMO, so I'd get the old school 98. A proven tank that did me proud for 5 years before being sold on to it's new owner 9 months ago....
I have never ran the 800, but I do work in an aquatics shop and thus have seen the system in the flesh. The lights feel cheap and the new hood has been made more complicated than it needs to be. The "feeding flap" is a real gimmic and the bit of hinged plastic the light is on flexes and bends when lifted. I wouldn't run the lights with anything on top of them for fear of it falling in....
The filter has had all the surface area reduced, making it higher maintanance on paper....
If you follow the manufactures guidelines, it will cost about £7 a month in filter pads for both. With a few "tweaks" you can get it down to like 5p.... Remove the carbon pad; it isn't needed. Get a new blue sponge in there. Same with the green ones.... After that, buy a bulk pack of pond floss and cut it into replacement pads. A bag will cost like £5 and will make like 1-200 pads....
The 98 has none of the problems of the 800 IMO and is a good solid tank. Lighing could be better, but heck it could be also on the 800....
HTH
Rabbut