You're not sure what you want. That is, you don't know what you want a laptop for.
The M1330 is an everyday portable machine which is not a desktop replacement but does most 'officey' things that people do, the media stuff (and with Ultimate, the M1330 is actually quite a capable media machine on the go) and some very light gaming.
The M1730 is a heavyweight gaming machine. Carry this every day and your back will be hurting soon. It is a desktop replacement, so it's big and heavy. If you buy this wanting a machine to carry to/from classes, be mobile, etc then you'll probably regret it - it'll end up spending a lot of time in your room.
I have a couple of M1710's, at least one of which will be replaced by the M1730 - in fact, I'll be placing the order on Monday when the quote is confirmed. However, I don't use the M1710's (which are, I believe, lighter by a bit than the 1730) as everyday carryabouts but as transportable desktops - i.e. carry from one desk to another and not as true 'notebooks'.
I don't even use an M1330-class machine (I have three M1330's, which won out in an Sony SZ choice mainly because it was only a bit heavier and did everything I wanted for a lot less - and it didn't come with a truckload of Crapware preinstalled) as everyday carryabouts, preferring lighter machines like the Sony G and TZ series, but the SZ / M1330 is the class of machine I turn to when I need a do-everythinger which is still very portable.
You need to figure out what you're going to do with the laptop and how you're going to use it before making the choice.