a DC-DC PSU is always a better solution for a computer (or any other DC device).
inverters should be avoided whenever possible. the only time an inverter is necessary for a PC is when the DC device draws more power than any [currently available] DC-DC PSU can provide. in your case you are using a 150watt inverter so that shouldn't be an issue.
most of the DC-DC PC PSUs are designed for desktop-type computers that use a multi-rail ATX PSU. laptops use a single-rail "power brick" PSU that outputs a higher voltage than an ATX PSU. you can buy a cheap auto/air adapter off eBay (if you can find one for your laptop) or you can get a good universal model like a
carnetix P1900 or P2140 which can output typical laptop voltage (18v, 19v, 20v).