There are a number of companies on the market.
I would lump most of the "silicone" manufacturers into a single pot.
SunPower has some of the highest efficiency (consumer) panels on the "common" market. However, I think they sell their panels in somewhat odd voltages. They are rated around 40 volts. I.E. Not recommended for a 12V system. Wasteful at 24V, and perhaps ok for a 36V system. You would very likely need a MPPT device to get the voltage to the desired point.
"Efficiency" is merely a measurement of how large a panel will be for a particular amount of power generation.
If you have a large, south-facing roof, and plan on putting flat panels that only will cover a portion of the roof, then efficiency is less important.
However, if you are investing in a solar tracking system, and/or have limited space, then efficiency may be more important.
I have a set of "used" Siemens panels. I believe they were originally installed on a mobile RV system, and their power generation SUCKS.
I don't know if these panels have suffered years of damage, or if Siemens panels inherently have problems.
My next set of panels will either be NEW, or UNUSED.
Many people are highly suspicious of "glass" based panels, "thin-film", or "flexible" panels.
There are a few companies coming up with a foil-based panel that report that their production methodologies are far less expensive than other types of panels. However, I have yet to see the promised $1 / watt panels hit the market.
You will find that the cost/watt decreases steadily with the increase in size of the panel. So, a 10W or 20W panel might be $10-$20 / watt. But, a 200W panel might only be $4-$5 / watt.
There are also a few more "radical" designs. For example, cells or panels with tiny holes in the cells to allow ambient light to pass through (skylights, partially obscuring windows). Another unique design can essentially be installed with regular roofing. A third unique design is a "double-sided" cell. I am a bit puzzled on the benefits, but perhaps there would be benefits for generation on cloudy days, and/or certain applications where the panels are mounted with good rear visibility.
The highest efficiency cells are produced by Boeing (Spectrolab) & Emcore. They incorporate a triple junction design, and run around 30%-40% efficiency. They are most effective with concentrators. Unfortunately, the cells are also expensive, and hard to come by. Because they are generally used with concentrators, they are also TINY. I could imagine, though, if you were severely limited in space (for example, on a solar car), then triple junction would be the way to go.