Artchie;
I've had experience with both. I've owned a 232 Gulfstream and fished out of SW Fla on a friends 258 Journey with twin 150's.
1.) RIDE:
The 258 will ride a little better than the 232 due to it's narrower beam. The 232 will "slap" some in a head or quartering sea due to it's being a "Widebody."
The 232 will be the better boat in a beam or following sea due to the aforementioned beam. It is less athwartship-sensitive than the 258 Journey.
The Gulf off SW FL, as you know, is infamous for it's short chop and does not have the long period swell of the Atlantic very often unless they are sprung from a distant storm offshore. Both your prospective boats will be fine in anything up to a 15K wind. Then the seas build over 2 ft and it gets uncomfortable, although certainly not unsafe. Your personal comfort boundaries will come into play here. Either boat can take more than you can.
On most days in the summer months with either boat, you can exit Gordon Pass or Doctor's Pass and run the coast to Marco or North to Bonita/Ft Myers. The Keys is an easy run with anything under 10Kt winds. You'll have to run offshore approx 10 miles around Cape Romano and then you can set a heading to Vaca Cut, Seven Mile Bridge, or run a charted course directly to Key West and come in the NW Channel. If you want to target Islamorada, you'll have islands and shoals to skirt in Florida Bay. At 30MPH, which those boats will easily cruise at, you can make the Keys in less than 4 hrs. under calm conditions.
2.) POWER:
AS I've stated many times on here, I am a fan of as much power as you can hang on a Grady. That said, twin 150's will be a great combo for the 258 Journey. I prefer 200's on the Gulfstream, but 150's work well on that hull too.
3.) TRAILERING:
As we talked about on your other post about your Tundra's capability, both boats are a significantly heavy pull for a 1/2 ton rig. My answer here is the same there; you'll be OK, but better off with a heavier 4WD truck. Getting the Journey will eliminate the need for overwide permits as the beam is a legal 8' 6".