Firstly the 1500kbps and the 3000kbps download speeds I believe refer to the local (or Singapore-based) sites.
Cos, to my knowledge, all the ISP's broadband are limited to 512kbps per connection for overseas traffic as they (the ISPs) have to "buy" bandwidth from the Singapore IX or Internet Exchange.
If it is really 3000kbps for overseas sites, I am sure it will beat all the other ISP by 6 times compared to a 512kbps.
For broadband you need to compare the pros and cons of the 2 major forms of broadbands in Singapore.
They are the Cable-based and ADSL-based.
As for the Cable-based,
a) They are easily available as most homes have SCV points.
b) They are easy to use, no need to "dial-up", as you are connected the moment you power on the PC and enter Windows.
c) The use of cable, means you need not convert your phone lines to digital and less "disturbance" to your telephones.
However, since SCV does not loan it's cable modems any more, you need to BUY them.
So, you BUY a cable modem and you can only use it for Starhub MaxOnline as there are NO other ISPs in Singapore which you can use your cable modem for. If you switch you will have to sell your modem.
It's slower than ADSL, (ok, I know a lot of people will say otherwise, I am a former SCV user (for 1 year) and it a current ADSL user (for 2 years) and I must say the upload and download for the ADSL is faster, my colleague on SCV also agree.)
Due to SCV's habit of bundling it's offers with Maxonline, if you do not subscribe to MaxTV, you will have to pay a bit higher than users of both MaxTV and Maxonline.
there is no real competition since it's the only cable-based provider and to switch will mean buying an ADSL modem and converting the phone lines to digital, so most won't.
As for ADSL.
The downside is.
It uses the phone line, so if you have a PC in your room you need a phone socket. And you need micro-filters for all your phones in your house, if they are using the same line as the ADSL. (unless you have 2nd line)
It's force you to convert your phone lines to digital and hence the above inconvience and any problems with your phone line will result in your internet disconnection or voice quality in the phones.
It is expensive if you tend to move house frequently, like if you live in a rented room. As you have to convert the digital line back to analog and convert another analog to digital. It costs $72.80, I think to "move" the connection.
you have to buy an ADSL modem (though the prices are cheaper now, some packages include a free USB one, with a contract)
The advantages
It's faster and adding a 2nd phone socket is cheaper than a 2nd SCV point if you do not have either in your room.
There are at least 2 competitors in the ADSL market and a price cut by one will most likely induce a similar cut by the other, and as a consumer you decide who to sign up with.
If you are unsatisified and decide to switch to another ADSL service provider, you can use your existing modem and DSL phone line with little extra costs incurred.
For me, my ISP, gave me a new price after 2 years of contract, which I must say is attractive, and I signed an extra 1 more year at the new lower price.
SCV's 2 months free package (abt $100+) will only subsidies the cable modem price. you need to think long term.
SCV's frequent maintainece and downtime, result in you not being able to download files overnight sometimes, as the downtime will kick in after midnight abt 1am and result in a broken connection.
It's more than prices than mattars for broadband service. It's the package deal and the long term service quality of the ISP to consider.
Cheap ISP with connection problems or slow speeds could make your broadband experience unenjoyable.