A good LNB performs better all round than others and of course to get better you pay more money which is what he is saying when he compares different LNB's on pages 6, 7 and 8.
If you lived in the UK most if not all the LNB's meet the standards he mentions even though they are now out of date and he should be looking at the Astra 2 specification rather than the old, to be retired, Eutelsat satellites.
You also have to keep in mind that the maximum disk size specified is 60cm for the Astra satellites servicing the UK after which your on your own and as we have seen there are no guaranteed results. Somebody 15km away can get excellent reception on a 100cm dish where as you could be struggling with a 130cm one. When you get to this level it is worthwhile looking at a better performing LNB like the Invacom which has definitely helped people who have been having reception problems.
In theory it is all down to the dish size and won't find anyone who disagrees. You should be able to any standard LNB but just increase the dish size till it works. However a good LNB can effectively add a couple of cm to the size of your dish and perhaps when used with a feedhorn of good quality you can make a 130cm dish perform the same as a 140cm. It all comes down to the price of the dish and practical side of mounting it. A 130cm dish will cost around 130 Euros, move up to a 150cm dish of reasonable quality and your looking at about 600 Euros, should you need to go even bigger to say a 180 cm dish you're looking at a grand. Then there is the installation cost, a 130cm dish will bolt to the side of your house, move to a 150 and 180 and you are looking at constructing a ground mount on a concrete pad which adds serious cost to the installation. So if you're on the edge of reception and suffer from a bit of pixelation now and again or you only need light rain to lose your picture it may pay to look at a better quality LNB and even a feedhorn.
One thing I didn't see him mention is length of cable. As he says you want the right amount of gain but if you have a long cable run due to where you can mount your dish even with a quality cable you may need a high gain LNB so that when the signal arrives at your decoder it is at the right level with maximum signal quality and lowest noise levels.
Other than that it is an excellent bit of work with some simple explanations which certainly helped me as I am sure it will others.