It seems there are a lot of choices this first gen and probably many more to come within the year as we see refreshes spurred on by new low powered Intel i5 processors and AMDs power sipping "Hondo". Both promise to up the anti as far as battery life, thinness and brute force are concerned.
Looking at tablets now there are basically two Windows 8 camps (well 3 if you count RT but nobody does) - the Intel Atom and the Intel i-series.
Almost every PC manufacturer in the game offers a Windows 8 Atom based tablet. IBM, Dell, Acer, HP, Samsung, Asus - you name it. They come in all sorts of flavors with all sorts of accessories (clamshell, docs, keyboard cases) and many offer digitizer options (pen). The Atom based tablets have a couple of major benefits and a few drawbacks as well so it really depends on what you want out of your tablet.
+superior size / weight due to low-power, fanless CPU
+superior battery life (many get near 10hrs)
+runs full Win8 o/s (not RT) so compatible with legacy apps just like the Surface
+lower price point (run between $499-$699)
-not as powerful as i5 processer found in Surface (struggles with more process/graphic intense apps but fine for day to day stuff)
-eMMC storage (its solid state but more like a big memory card so reading/writing to drive can be slow)
-screen resolution seems to be limited to 720P (not sure if its cost or limitation of Atom)
-USB 2.0 and 2GB RAM (which is a limitation of Atom)
Fewer companies offer i3/i5/i7 based tablets, such as the surface but there are still plenty of flavors and plenty of accessories. These tablets are closer in spec and price to top end ultrabooks so you are really getting a convergence device the blurs the line. A single device that can do it all.
+power of a high end ultabook
+power to run cpu intensive apps smoother than Atom but still probably not going to play Crysis3 on it.
+1080p screen resolutions
+true sata3 ssd drive for ultrafast read/write speeds
+4GB of RAM typically
-larger/heavier form factor due to extra heat from cpu and fans for cooling
-poor battery life (about half of what you can expect from Atom based tablet)
-high prices (I think cheapest is Acer W700 w/ i3 CPU @ $799)
So, there really is no true winner at this point. It comes down to what you value most and will be using the tablet for the most.