I have two new question
1 How heavy of a cut can you do on a bench vs standalone planer on oak or equivalent hardness of wood?
2 Am I better off spending less on a planer and getting a surface sander instead
#1 Interesting question...heavy cuts tend to create a rougher finish than light cuts. If you are working with hardwoods, i.e. maple and/or oak, then you may find the wood chipping out rather than smooth cuts. Softwoods, i.e. Douglas fir, hemlock and/or poplar, may be planed with a heavy cut and have a smooth finish.
I have a Grizzly G5850Z 20" planer with four (4) knives. It has a 5hp cutter motor and a 2hp drive motor. It works great with softwoods and most hardwoods. I planed some of my figured maple with it and the finish came out very rough. Instead of hand planing the figured maple and then sanding it, I took it over to a friends wood shop. He has an 18" Woodmaster surface planer with a spiral head cutter. We ran the same pieces that I had planed on my planer on the Woodmaster. They came out very smooth. Very little sanding with a 220 grit paper was required.
So, I would be looking more for the smoothness of the finish rather than "how heavy of a cut". If you are using a spiral head cutter, you will not have to do as much sanding. You may be able to use a hand plane, card scraper or hand sanding block for the final smoothing.
I do a lot of re-sawing with my band saw. I try to get the thickness of the board within 1/4" of my final thickness. I can then remove up to 1/8" on one side of the board with my jointer and 1/8" from the opposite side with my planer. I usually do not take off more than 1/32" at a time. That calculates to about eight (8) passes total for both the jointer and planer. This creates a very smooth finish with minimal sanding. If I was to try to take off more than the 1/32" per pass, I would have to do a lot more sanding for the final smoothing.
If you are looking to save some money, you might want to check in your area for businesses that offer planing services. A few of the wood shops in Portland, Oregon offer planing services at reasonable rates.
There are a couple of schools in my area that have planers that are available to students. You could try out different planers and see what works for you.
You could also find about a Woodworkers Guild in your area. Here is a link (http://www.guildoforegonwoodworkers.com/
) to one in Oregon.
#2. I would spend more money on a better planer. Every wood shop has to have a method for final smoothing of the wood. I have a couple of sanders, but I prefer to have the wood smooth before I start with a sander. A good planer is going to do that for you. Final smoothing can be done with a good hand plane, scraper or just a piece of 220 grit sandpaper on a $5 rubber sanding block. If your planer leaves a rough surface, then you are probably going to spend more time and effort sanding the board to an acceptable smooth level with a powered sander.