Benefits of York (in no particular order):
1. 8 buildings of the York Fairgrounds filled with trains (3 dealer halls, 4 member halls, and a hall dedicated to a modular layout). You can find anything and everything from high-end scale brass down to the simplest toy trains, as well as scenery, other types models, detail parts, electronics, tools, books, clothing, videos, real train memorabilia, all sorts of cottage industries, and a lot more. Plus, UPS sets up a temporary shipping center on site to make it easy for out of town people to ship their goodies home.
2. Access to all of the major manufacturers. You can talk directly with company officials and see their newest products and production samples before they hit the LHS shelves.
3. Informative seminars on just about every subject, including the excellent layout building meeting that was started and is run by a group of fellow forumites and sponsors, and the Friday afternoon OGR Grandstand Meet where the major manufacturers give short presentations and speeches on what they are up to (news mixed with a lot of good-natured fun).
4. Social interaction with thousands of other train enthusiasts, including the OGR Thursdays at Friday's (TGI Friday's on Kenneth Road) gathering on the Thursday night of York. Always a fun time, and you get to meet lots of fellow forumites in person.
5. Pumpkin funnel cakes. 
6. If you have a few days to spend, you are just a short drive (less than an hour) from Strasburg, PA. Strasburg is the home of the Strasburg Railroad (tourist steam), the PA Railroad Museum (tons of great and historical locomotives and rolling stock), the Choo Choo Barn (a great layout that shouldn't be missed, and it is situated next to a nice train store), and the TCA Toy Train Museum (free admission for TCA members). There are also a number of outlet complexes nearby for non-train shopping, although there is a train-themed store in one of the outlets. And in the other direction from York, Gettysburg is not far for the Civil War buff (and the Gettysburg visitor info center is in a restored RR station 
).
As for other TCA membership benefits, there is the quarterly magazine (not much interest for scale modelers, but I find it interesting from a historical perspective), the ability to purchase exclusive, members-only merchandise (mostly non-scale stuff, but occasionally something pops up of use to a scale modeller), and members-only buying and selling both in an on-line exchange and in print (another quarterly mailing).
As always, you will be the sole judge of whether or not membership has something to offer. Also, keep in mind that you can go to York one time as the guest of a member (and many here on the forum would be happy to sign you in).
Andy
