@maff20
Flashlab summed it up pretty well. I personally would go for the Blizzard 030 with 32 or 64MB ram - it'll make some games run a bit quicker (eg Wing Commander, AB3D, Flight Sims) and won't compromise compatibility.
Plus the extra RAM, which you don't normally get with just a RAM card (I believe most RAM only cards are 4/8 MB) will assist in making your whole Amiga experience better, WB and Scala for instance.
I just think the Blizzard 030 card will give you that flexibility just in case the RAM card doesn't; but then again, it does depend on the budget.
Rude!