i think ethier one would be good if setup right for the grass.
the important thing is does your lhs carry the parts for ethier one also if the guys at your track race the same buggy you have helps with setups and parts.
i have a rc8t not a rc8b so il give you the cons.
the cons
1. the "plastic rear camber ball links" tend to flex and can cause problems its done it to me so i remmend boiling them in water to stiffen them up.
thats about it really acutally .
as for which one is better on bigger jumps etc im not sure .