My creatine bottle (I usually take tablets) says subjects who took 1.25g of creatine increased their leg press 1RM by 54lbs, subjects who took 5g increased by 52lbs, and subjects who took the placebo didn't increase. So, less is more with creatine?
Creatine doesn't have an acute effect. Its efficacy is dependent on whether or not the muscle is saturated with it. Taking creatine, in effect, will increase the amount of creatine phosphate in the muscle, in order to donate the phosphate to ADP to make ATP.
Regarding your question, once the muscle has become saturated, the dosing protocols used in your question are more to maintain the levels of creatine phosphate being stored rather than dosing to bring about more of a desired effect. Again, creatine's effectiveness is dependent on the muscle being saturated, rather than how big of a dose you take at any given time. 3-5 grams is recommended once the you've reached saturation, with the higher end being for individuals with a higher amount of lean muscle tissue.
Creatine is one of the most highly research supplements on the planet. It has also been shown to be quite effective for a myriad of different effects that go further than just increased muscular power output. To reiterate, it is safe and effective and likely has a place in your supplement cabinet. As mentioned above, muscle needs to be saturated with it in order for it to be effective. You can go about this in two ways: 1. Load it for a week by taking 20 grams/day (four 5 gram doses throughout the day) or 2. take 5 grams per day post workout continuously for as long as you want. Creatine doesn't need to be cycled either.
As for type, just get monohydrate. There are many different types out there, but the studies on mono seem to be the most reliable and it is also the cheapest. Don't go for big name brands that have small servings, claiming their product is superior. It probably isn't. You can find bulk creatine monohydrate on amazon.com for very reasonable prices.