others will disagree, but i think the 3.4 is total crap.
first and foremost it barely makes more power than the v6...at 235HP to the 6's 220. its an interference design (the 3.0 is non-interference) that is known for spinning the sprockets off of the cams, causing major internal damage. i also prefer the 6's iron block to the 8's aluminum one.
the 3.4 is a duratec platform, which means one would have to use a 2.3 tranny behind it rather than a 3.0 one. ive heard the 4 banger trannys may be slightly weaker and have closer gearing than the v-6 units (havnt ever verified these statements).
for the slight power loss, ill take the stouter and more reliable v6.