Keep in mind that the OP wants to buy a DS Classic.

An Acekard + EZ3in1 is a far better combination than a DSTwo alone for the DS Classic/Lite as far as GBA games are concerned, as it uses both SLOT-1 and SLOT-2 to make use of the DS's native GBA Support, unlike the DSTwo which uses external assets to emulate the GBA. It's faster, more compatible and simply more stable. Moreover, a 3in1 also offers Rumble Support and is a RAM extension for the DS and DS Lite alike, which may be useful in some homebrews and allows the user to use the web browser.

Now, when it comes to the rest of the OP's desires, SNES emulation in particular, a DSTwo is indeed a better solution.

• NDS Support
  The DSTwo has a slight edge over the Acekard 2i due to its built-in hardware Anti-AP, however AKAIO patches are on-track most of the time.
  
  
• SNES Support
  The DSTwo wins hands-down, the DS alone is not capable of proper SNES emulation. Not that the DSTwo's emulation of the SNES is perfect, but it's acceptable.
  
  
• GBA Support
  Acekard 2i + EZ3in1 is the winner here - native support always beats emulation.
  
  
• GBC/GB Support
  It's a tie - both solutions will give you equal results.
  
  
• NES Support
  Pretty much a tie as well - I never encountered any huge issues with NES emulation on my Acekard 2i.
  
  
• Battery Life
  The DSTwo, depending on the settings of the external CPU, is quite battery-draining. An Acekard 2i will allow better battery life, which is a factor before making a purchase.
  
  

Now, I'd like to stress that the DS - with a DSTwo or without one, is not the best device to emulate on. Its assets are limited and its native resolution is relatively low, often resulting in the emulators having to scale the image or crop it. If I were to recommend a device solely for the purpose of using emulators, I would say "get a PSP" - they're affordable, comfortable and much more powerful than the DS, resulting in better emulation capabilities. However... You can't enjoy DS games without a touchscreen, so that's a no-go for the OP.

In the end it's up to the OP. To conclude, the DSTwo does offer better capabilities, apart from GBA Support, RAM extension and Rumble, so it's likely to be a better value.

This post has been edited by Foxi4, Tue, September 11th, 2012 at 16:42