I have tried the internal filter, and I did not find it to be a good match for a betta. It basically takes in water through a sponge and spits it out through a powerful jet which tends to knock bettas around in the water because of their long flowing fins. This would be more suitable for smaller fish without a lot of finnage. Also, any debris that you were hoping this filter would suck up simply get stuck to the outside of the sponge, so when you take the filter out to clean it or turn it off all the gunk on the sponge goes right back into your water.
I still suggest getting a small power filter--the debris are easier to clean out and they generally provide a lot more space for bacteria. Also the current can be baffled using the soda bottle trick. They're not any more expensive than the internal filters either. Case in point: http://www.fosterandsmithaquatics.co...3578/3579/3608
It's still good idea to look up reviews on these on other websites--I don't have much experience with brands other than aquaclear and marineland.
Given the price difference I would go for the stealth heater, they don't have an indicator light (iirc) but they're not made of glass, so they take a lot more abuse than the glass hydor theo would. That's the only major difference. Also, you might want to take into account the size of the tank you're getting versus the size of the heater--25 watts is sufficient for 2-6 gallon tanks, and 50watts are usually used for 10+ gallon tanks. If you end up getting a shallow tank like the marineland eclipse 3, for instance, you'd probably have to lay a 50 watt heater sizeways on the gravel rather than have it stick to the side straight up and down because of the length.