Platinum team help..opinions needed..

So here's the deal. about a week ago I caught my first ever shiny. It was a ponyta (now Rapidash) Hardy nature with all around mediocre IV's (mid teens to low twenties..but nothing lower than 12). It also has Flash Fire. It was a decent find considering he could wall the fire attacks launched towards my Scizor.

Now, today while training my Lucario I ran into a shiny gastly...timid nature.

The choice should seem obvious, but here's the problem - Gastly has 20-25 in Speed IV's which is fine enough for in game (and hopefully the battle frontier). However its special attack IV's are 0-7. Should I still use him over Rapidash?

I don't really expect to compete much over wifi, the farthest I plan to go after the elite four is the battle tower and maybe a few other frontier sites. I EV train, but dont have the patience to get perfect IV's...as long as they're good enough.

If this helps, here is my team so far:

Torterra - Relaxed
Stealth Rock
Leech Seed
Giga Drain
Earthquake

Staraptor - Jolly
Fly (because I need it)
U-turn
Close Combat
Quick attack

Scizor - Adamant
Swords Dance
Pursuit
Bullet Punch
U-turn/Brick Break (undecided)

Lucario - Modest
Vacuum Wave
Aura Sphere
Dragon Pulse
Sahow Ball

Tentecruel/Vaporeon/Kingdra/Starmie (Undecided)

Slot 6 is for either Rapidash or Gengar.

Obviously the biggest problem with this team is bulky waters...which Gengar can cover with Thunderbolt..would he be strong enough to succeed though with low Special Attack?

It's between these two..dont want to breed for better IV's or another shiny gastly.

Who should I choose?

Okay so you're walled by bulky waters so the best choice for your team would be Starmie who learns Thunder and Thunderbolt Via TMs and walls almost every water type in 4th gen. Starmie can also take Fire type moves well so Rapidash wouldn't be necessary.

Gengar's Special Attack at lvl 50 (Non boosted or decreased by a nature) is 135 - 182 (135 being 0 IVs, 182 being 31). Rapidash's attack stat is 105 - 152. So you're dealing with around the same offensive stats regardless of which you pick.

Now let's look at type coverage. Your team isn't exactly weak to fighting (Staraptor is pretty bulky and can take a fighting move and Starmie can also take a fighting move or two.) So Gengar's fighting immunity isn't necessary while it's helpful. Nothing on your team can take a strong fire move too well except Starmie who can still be THKO'd by physical fire moves. Gengar can't take fire too well either.

Offensively Rapidash isn't the best pokemon. Its move set seems pretty limited but it does have decent defenses. Even though you may get a free switch in on a fire type move, you won't get to use a fire type attack being that you'll most likely be facing a fire type so your flash fire boost is pointless. You also may not be able to revenge kill it in one hit (or Two). Gengar on the other hand can usually switch into a fighting or normal move and proceed to OHKO it with most of it's STAB moves (Or Psychic specifically for fighting types).

Your team (assuming you decide to use Tentacruel) would be extremely vulnerable to anything with a ground type move which is incredibly common. Rapidash would only add to that problem and your only defense would be Staraptor and maybe Scizor.

Your team /is/ lacking a fire type though and Gengar can provide some pretty redundant coverage with it's standard movesets. So the choice is all up to you. Hope this helped.

Just a word of advice: Using a shiny just because it's shiny isn't a good idea. They're usually just trophies so using them isn't really necessary.

Okay. Thank you for your help. I just may have to store both in the PC and just add a bulkier pokemon to the team. Maybe Lickilicky? It packs Power whip for waters, nice defenses all around and can learn a nice set of moves.

thanks :)