Bosch really sucks, Makita 5'' random orbit is my vote. J.

I have to disagree about the Bosch RO sander really sucking. I have 2 Bosch RO's and they're actually quite good. They are WAY BETTER than Porter Cable, DeWalt, or Ryobi, which I have also owned in the past.

There are many different models of RO available from every manufacturer. Check the speed of the motor. They're rated by orbits per minute. 12,000 OPM is good. I would not get one rated for less. The Bosch models I own are the 3107 DVS and the 1295 D. The 3107 is really powerful, it would work great for sanding a deck. The 1295 D also has nice power, but it's a bit smaller and lighter. I use it for finish sanding. Neither model leaves swirls as long as you let the tool do the work. Swirls happen when the tool is bogged down by the operator using excessive force which prevents the motor from orbiting randomly. The sanding pad needs to spin freely to leave a nice finish without swirls.

Thanks Aidan, I probley ment the 5'' Makita takes off material way better, IMO , than any bosch I have used. Not that the Bosch dident work or hold up, and I dont know at all why but thats been what I have seen. J.

How big is your deck? Ours is just under 700 sf, so we rented a floor sander from HD and just used an ROS for the edges the big guy couldn't reach. It takes a LONG time to hand-sand a big deck. We didn't go through an inordinate amount of sandpaper. Can't recall precisely how much.

We just sanded and stained our deck. Used a belt sander for the floor, then an inexpensive 5" orbital sander to get the smaller parts and the railings. No swirl marks, but a nice smooth finish. I would skip the liquid stripper and power washing...unnecessary steps unless you have layers upon layers to remove. The sanding makes a nice smooth surface for great stain adherent. I like to use 80 grit on main parts of the deck and 120 after using 80 on the railings. Just give it a good rinse after, let it dry and you are ready to stain! Good luck!

I have to agree with Aidan. I have the 3727DEVS from Bosch and it's a champ.

Here is a link that might be useful: Bosch 3727DEVS

Just got a Festool sander. WOW! This thing is awesome for woodworking. I wouldn't ever use it on a deck, though. It's designed to work on a flat surface, and forces the operator to use correct technique. If you don't hold it properly, it won't stay on the work surface! You have to keep your hand steady on top of it and apply minimal pressure, move slowly and let the sander do its thing. It leaves no swirls on fine veneer, even with 120 grit. And it doesn't round the edges at all. What a nice tool to have for inside the shop.

My point is there are different "best" random orbital sanders depending on the task at hand.

I've heard great things about the Festool...especially the dust collection. I personally have 3 5" ridgid ROS, and it's the best that I've used...and I've used many over the years.
You can't slow it down; it has a 12' cord; great dust collection, even without a vacuum attached; and I love the light in the plug that let's you know that the power supply works. One more thing, it has an icon on the plug so that you know it's for the sander. If you have a lot of tools plugged into a power source, it's good to know which one you're unplugging.
I use 50 grit paper on Ipe decks.

If you already have a Bosch ROS, it should do the job.

steve

In case you are looking for a few times home uses at most i recommend u going with B&D BDERO100 or Dewalt D26451 which are really cheap options and offer acceptable quality for home use. In case you are looking for professional orbit sander for professional work with great quality and dust collector that would be Festool 57187 which wins over all sanders in the long run, but is little bit expensive if you buy it for home only. There is also a great random orbit sander buying guide which can help you explore and read about all the other brands available at the US market, however i dont recommend reading about them all because you will get confused.