You really should check out THIS book:

From soft to hard (off the top of my head… someone can correct me if I'm wrong)

• Pine (softwood, closed pores, very blotchy if not treated first)
• Cedar (softwood, closed pores, can be blotchy if not sealed)
• Mahogany (hardwood, open pores, finishes evenly, fairly easy to work with for hardwood)
• Cherry (hardwood, closed pores, can be very blotchy sometimes, easy to work)
• Walnut (hardwood, open pores, finishes evenly, works nicely but moderately hard)
• Oak (hardwood, large open pores, finishes evenly but with contrast between earlywood/latewood, pretty hard stuff)
• Birch (hardwood, closed pores, finishes nicely, very hard)
• Maple (hardwood, closed pores, finishes nicely, "hard maple" is extremely hard, "soft maple" is easier to work)

I've never worked with aspen, our local stores and lumberyards don't carry it.

 

Here's a post that covered the subject really well
http://lumberjocks.com/GaryK/blog/4703

and another great wood site that has thousands of wood photos and tons of info

http://www.hobbithouseinc.com/personal/woodpics/

As far as blochiness check out charles Neils web site or ask him questions about finishing.

http://charlesneilwoodworking.com/

 

Here's one reason the Janka charts seem to be different. I copied this from the wikipedia page on the subject.

The hardness of wood usually varies with the direction of the wood grain. If testing is done on the surface of a plank, perpendicular to the grain, the test is said to be of "side hardness." Testing the cut surface of a stump would be called a test of "end hardness."

The results are stated in various ways, which can lead to confusion, especially when the name of the actual units employed is often not attached. In the United States, the measurement is in pounds-force (lbf). In Sweden it is in kilograms-force (kgf), and in Australia, either in newtons (N) or kilonewtons (kN). Sometimes the results are treated as units, e.g., "660 Janka".

To convert the United States pound-force (lbf) units to newtons N multiply pound-force by 0.453 592 37 then multiply by 9.80665 (1 standard g in units of m/s2). Janka hardness N = (lbf x 0.453 592 37) x 9.80665 OR multiply by 4.44822161526. To get lbf from N, multiply N by 0.224808943099736.

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I have also noticed the discrepancy of the Janka Scale ratings posted online and suspect that the original sources have been copied and pilfered without much accuracy. I have also found that woods of different sub-species grown in various areas and even different parts of the same tree can have different densities, such as the crotch or other figured area of wood, so it's not that easy to determine the hardness of each wood, although the Janka Scale can give a good idea of how hard the wood(s) you are working with can be.

You need to cross referrence between the written and the hands-on resources to determine what is the best wood to work with. The application and design are also to be considered, not to mention talking to a craftsman who has first hand knowledge can't hurt either. Your local lumberyard or sawyer who actually knows his stock (not a paid-per-hour employee who doesn't have a history with lumber) would be a good source of knowledge.