Sump Tanks Yes Or No

pros are that they can house all the tanks equipment e.g.heaters too, they have increased space for filter media too, flexibility comes into this too e.g. housing juvenile fish
cons are risk of flooding during power outage (can be mitigated against) and can be tricky to set up, increased evaporation including damage to cabinet, loss of co2 if your planning to inject it, loss of space in cabinet
(I'm sure there lots more that others can add... I've never actually had a sump, these are just from the top of my head!)

can I ask though, why you want a sump over an external filter (or two)? Sumps are more common for the marine side of the hobby. I'm running these... https://www.oase-livingwater.com/en_GB/indoor-aquatics/products/p/filtosmart-thermo-300.1000078360.html

I'm looking at all options, I just thought sumps were the way to go,  I'm looking to get the filters and heaters out of the tank and also because of the size of the tank I wondered about capacity...  it's 600ltrs so that's why I should run two (300) filters ? [I know It might be a silly question, but I don't know if that's right]
Those thermo filters look good, do you need to back up the heating or are they good
Ta

Yes if you ran 2 300s you would have enough filtration for the 600. The heating would be backed up in a way if you had 2 filters

Of course you could also switch the standard intake etc out for glass Lilly pipes for a more discrete look...