Cheaper than a cab, too! They are timetabled at 20-30 minutes to Gare du Midi, via Gare Centrale and Gare di Nord.

The only issue about the airport trains is that they are a bit unevenly spaced out (you might go for 30 minutes without one). They are punctual though and a quick look at the SNCB/NMBS timetable will get you the info you need. You can also buy tickets on the train, saving the need to queue or use the machines (which are useless in any case unless you have a Belgian issued bank card...)

For tourism I would go for Le Meridien if SPG is your programme. Very convenient as its walking distance to everything central and across the stree from gare Centrale metro and railway station. Avoid hotels in the Schuman district - fairly handy for the centre (there's a Metro link) but dead at the weekends (think staying in La Defense in Paris, or the City in London).

I am something of a regular at the Four Points and find it a serviceable hotel. It is not in an obviously touristy part of town though lots of ex-pats live in the area and there are some decent high end shops about. Get a taxi when you first arrive so you get your bearings. There are trams into town but they only run every 20 minutes on Sunday and the frequency is not much better durng the week. You can walk into the city centre but this would take 30-45 minutes.

Another option (more for the location than anything else) would be the Jolly Hotel which is on the main square in the Sablon district, a 10 minute walk from the main city centre area. the hotel is serviceable but it is really the location you pay for here. The square is really atmospheric and if breakfast isn't included the Le Pain Quotodien across the square does really good breakfasts and light lunches.

On the Eurostar v Plane debate, I always take the train unless I get priced out
(typically happens if booking less than a month in advance). This is way more convenient than braving the security queues at T4 and BRU. I generally try to book at least one way in Leisure Select, their first class product, which is cheaper than an I class CE return on BA.

In fact, if I have to fly I will typically look at VLM out of LCY before trying BA or BD.