as far as i can see both the Kingston and the Crucial RAM on that page are made up of 72 modules per DIMM... the apple spec sheets specify maximum 32 modules per DIMM.
i can't find 32 module FB-DIMM DDR2 PC2 5300 anywhere...
apart from that, i've read good reviews of FB-DIMM DDR2. negative point is that for the moment almost no-one is making them, being that they are destined for "mission critical servers", but most manufacturers have announced products.