Mikes response is exactly right as far as I'm concerned.
The first priority is that the oil is changed, and changed often.
You will not get more oil out by sucking it out. In some cases you MIGHT get as much. The belly pan is really no problem at all. Just get an 8mm nutdriver or some such and spin out four screws, no big deal at all.
Now for my personal preference. Anyone who has read more than about five of my posts probably knows that I am a total mental illness level fanatic when it comes to oil changes.
I only drain oil when the oil is at operating temperature, which is after about 17 miles of driving minimum. I do it on a Friday night, pull the plug and let it drain all night. The last few drops that you get are the nastiest of it all, the real sludge. By draining it hot, the contaminants are churned up in the oil rather than stuck to the innards of the engine. I also change filter with every oil change.
As Mike said, the underneath method gives you the chance to see if there are any leaks, and look for anything that might be about to fall off.
Change oil hot and change oil often,