Solar panels are available in 2 varieties, Monocrystalline or Polycrystalline.  The type best suited to your needs depends on your application and budget.

Monocrystalline panels are made using single crystal silicone, which are typically larger crystals than found in Polycrystalline panels. Monocystalline is made up of a purer form of silicone making the crystal continuous and free of any grain boundaries (the join between the grains of silicone). This makes Monocrystalline the more efficient light absorbers, by up to 15%.  The catch is Monocrystalline is more expense to make, due to the manufacturing required and the fact that the silicone crystal is all from one source.

Polycrystalline panels are made up of multiple silicone crystals from a variety of sources.  The silicone is still quite pure and very effective for use in solar panels, with a cheaper manufacturing cost than Monocrystalline.  Polycrystalline panels are available at a lower consumer cost due to this, but they are not as efficient as Monocrystalline.

The debate comes down to budget and location or available space.

If space to install your solar panels is limited, a higher efficiency panel such as a Monocrystalline panel would be a great option, but would come at a higher cost.  If space is unlimited, Polycrystalline panels would as the amount of space for solar panel installation would make up for the reduced efficiency.

That said, this is not applicable to all situations, and with solar being so important to our energy needs, a variety of systems and applications are available.  A consultation with a reputable solar company and technician will be able to determine and tailor a solar package best suited to your budget and needs.