Gidday Shilo,
My wife and I love our SX18, we take 4 - 6 adults on it often with no problemo at all. The other day we had 4 adults on board and hit 51mph. That is plenty fast enough for me. When we use the biscuits we get onto plane really fast and has no worries with the weight behind it. We have the 190hp V6 Mercruiser with a 4 blade SS prop so hole shot is great.
Without biscuits we get onto plane in 3 seconds easy - I installed the trim tabs (with thanks to MikeyT) which makes life real easy particularly when going slowly - no chining now.
We had our boat moored beside a bayliner the other day, same size same colour scheme and age, and I tell you ours had a bunch of better features than that boat.
The other guy was really impressed with the extra little features ours had that his didnt.
I agree with MikeyT that if the sales men are bagging these boats then its just salesmen talk.
You really need to take a few for a blat on the lake or river and make up your own mind. But value for money I would certainly buy another Mariah particularly before a Bayliner.
Dont forget the motors will all be the same, so thats a no brainer there. Our dash board layout is definately the best of all of them, the stereo is conveniently hidden away and really easily accessable in it own glove box - I think mine is the Sirius ready one (but we dont have Sirius radio stations in Australia !!). But the sound system is great. The fact that there is a seperate anchor well is also a bonus, saving you trying to find a spot to put your anchor somewhere.
The side floor pockets are great too, we put heaps of stuff in them, I know Tahoe dont have these so again you have to find a spot for stuff that you would want to get your hands on easily.
We had a few minor little problems when we bought ours, but it was second hand so you gotta expect this sometimes. It was all fixed under warranty anyway so no cost to me

Good luck with your purchase no matter which way you go.
One other added bonus of buying a Mariah is joining this great forum to get all your answers and have some extra fun.