It's a hard comparison because its like comparing Apples to Oranges, some like Apples some like Oranges. Plus your not saying how wild you want to go which would play a big part in the decision...
I can tell you this... I've had 5 Supercharged Fords in a row now and have tried Stock Eatons, Ported Eatons, Magnum Powers, 2.6 KB, 2.3 Whipple, and now a 2.8H. There is NOTHING like the INSTANT Power & Boost a Twin Screw or Roots Supercharger will give you, (especially over 20lbs of it

)
Not saying the
Centrifugal arent Bad Ass too, amof there are some
advantages with the Centrifugal. What I'm saying is they clearly perform differently that the Roots or Twin Screws. I'm going on the assumption your talking about a P-1SC at modest Boost and not a F-3 that can handle 2500 HP
With that said if your 98 is a stock block and or has high miles the Centrifugal may be a better choice for a few reason. #1 you can install the entire kit in 1 day and be driving it that night, #2 you can drive around with the Centrifugal 24/7 and never even know it's there. AMOF in most cases you wont even go into boost unless your really step into it.
#3 It's alot easier on a stock block because it's not in the boost 24/7.
The good news is they still give you the massive power gains and low ET's you want at the track when you do really step into them.
Here's a before and after on my old 99GT. I installed it in one day and cleaned the entire engine compartment. Not the nicest looking but I bought a used set up for a Cobra and had to make it fit a GT