Having owned & used both tools I would say the best thing to start with is definitely the Combination Sighting / Cheshire tool, this tool can guide you in every single aspect of collimating your reflector. Make sure you do get the Combination tool, it makes it much easier.
One thing the laser collimator cannot do is to help you correctly adjust how far up or down the OTA the secondary is, ie aligning it square on to your focussor, and as that's the first step in the collimation process (and luckily the one that requires checking far less often than the other 2) that's why you should start out using the Combination Sighting/Cheshire tube.
Once you have everything tuned up using this Combination Tube then you can use a laser collimator to quickly and easily check / touch up the angular adjustment on both your secondary and primary mirrors before an observing session (ie after transporting your scope in the car, etc). Again don't get the "simple" version, make sure you get the "deluxe" type,ie the version that has the return beam & target. When you use it you will instantly see why it's MUCH better.
IT'S IMPORTANT TO KNOW THAT OUT OF THE BOX THE LASER COLLIMATORS THEMSELVES ARE RARELY COLLIMATED!
To be successful in collimating with these tools the laser beam must leave the body of the collimator dead straight! There are 3 small adjusting screws (smallest driver in the jewellers set I have) that control the exit angle of the beam. Best method I have seen to adjust these is to hammer 2 pairs of nails into a piece of wood in such a way that in each pair of nails one leans across the other, forming an X support. Position the second X so that each X supports one end fo the collimating tool. Point it at a wall at least a couple of metres away and slowly rotate the collimator whilemaking sure the wood / nails do not move. If collimated correcty the point where the beam hits a wall will not move (place a tiny dot / bluetack to make sure) but if the beam moves around to from circle whil the tool rotates then it needs collimating itself. Adjust until the beam doesn't travel anymore!
There is also the "Barlowed Laser" method of collimation which I haven't used yet, as far as I know that method replaces the normal usage of the laser collimator and as such still can't help guide your adjustment of the secondary mirrors position relative to the focussor.
When I started out to learn the mystical art of collimation I found a fantastic collimation guide written in easy common lingo by a retired ex-Navy guy in the States, his guide was the best I have ever seen bar none, if I can find the link I'll post it.
I hope this all helps.
Buying a quick Collimator
(47 Tuc for the first time.. yay. Resolved very well even in my 9mm). Yes I know collimation should be checked every time I get it out...
