Better Riding Shorts or Better Seat?

If by 'padded' you mean some great big thing with inches of padding then NO!  You're likely to have serious chafing issues.

I'd probably start by trying some new shorts - if it doesn't solve the problem then try a new saddle (and you'll just have an extra pair of shorts).

Are you having general Soreness or is there numbness in there too? I am not familiar with the stock seat on that bike but in general you will want a harder seat with the proper cutouts in it for the best circulation and to control that pain. Bike shorts could help as well but there is a lot to go into with that and a lot of it comes down to personal comfort. are you currently using bike shorts or just an old pair of running shorts or...? Also of note is have you had a proper bike fitting? if not it could also be the position you ride in currently is more irritating and adds to much pressure in the wrong spots.

 anyway some things to consider with this problem.

The Onix I had (or still have, but highly splintered) had a decent Selle Italia saddle that I kinda liked, but that's a highly personal thing.  I've heard it said that you keep the stock saddle until you decide what you don't like about it, then get a new one.

Assuming you have a proper fit and quality bike shorts (BIBS!), you can probably go to your LBS and try a bunch of different saddles.  Most places are pretty good about letting you borrow one for a week to see how it fits your backside and bring it back if you don't like it.  Padded saddles are for old ladies on 3 speeds at the beach.

Start with a re-evaluation of your fit.

If you race in a tri suit the padding will be less than cycling shorts and in that case changing shorts may not benefit you come race day.

If your fit is solid and you still have pains then I might suggest looking at the saddle.

Thanks for the comments.  To clarify...I have been fitted professionally for the bike and I feel really good in the seat.  The tenderness happens on longer rides (25 - 50 miles).  I don't really notice this problem in the Tri's that I've done probably due to the short bike (12 - 18 miles).  I train in bike shorts and use tri shorts for my tri's.  I'm guessing that the longer rides are a factor and that I will first try a new pair of quality riding shorts.  If that doesn't work, then I'll look into a better quality seat.

Thanks again for the quick response.

The last two months I've been riding about 80 miles a week (15 mile/Tuesday, 25 miles/Sat, and 40miles/Sun).

So you are getting some time in the saddle, which is good.  So it is not necessarily lack of seat time.

Where exactly is the painful area?

Edit:  Aside ...... where is Easton?  Easton as in the Eastern Shore of Maryland Easton?

Easton, PA which is about an 1 hour north of phily right on the Delaware River.

It is just a gentle tenderness where my body contacts the seat.  It goes away the next day.  Most noticeable on the long rides toward the end.