Are SNPs or SSR copy number variation mutations more prominent?
It's not really clear to me what you're after when you ask about how prominent or dominant these two kinds of variations are. But let's look deeper.
Guichoux et al. (1) say:

There are two main differences between SSRs and SNPs. First, SNPs are more numerous than SSRs in the genome of most species. On average, in the human genome, there is one SNP every 100–300 bp (Thorisson et al. 2005), com-pared to one SSR locus every 2–30 kb (Webster et al. 2002), depending on how SSRs are defined (Kelkar et al. 2010).This can be important for genome-wide association studies but not necessarily for other applications. Second, the mutation rate per generation differs drastically between the two marker types. SSRs have mutation rates ranging from $10^3$ to $10^4$ per locus per generation (Ellegren 2000), compared to about $10^9$ for SNPs, i.e. several orders of magnitude lower. As a consequence, SNPs are typically diallelic: In humans, &lt; 0.1% of SNPs are triallelic (Lai 2001).In contrast, SSR loci generally have high allelic richness, often in excess of 10 alleles.

Based on these numbers, SNPs occur perhaps 80 times as often as SSRs.  Is that more prominent?
An SSR is larger than an SNP, covering perhaps one hundred to several hundred bases versus one base (by definition).  An SSR locus also occurs in multiple variants, e.g. having a copy number from a wide range, versus only two possible variants that usually occur for an SNP locus.
The mutation rates are substantially different, apparently typically 5 orders of magnitude more frequent for SSRs than for SNPs.  Note, though, that mutation rate does not directly affect the frequency of variants seen in the genomes of extant organisms: the variants present are a result of the filtering of mutations by the forces of selection.
Note also that all bases are subject to mutation, thereby producing an SNP, but SSR mutations only occur where a repetitive sequence already exists.  (Also, the likelihood of mutation becomes significant only when the existing sequence has more than a few repeats, as the mechanism of mutation depends on this.)
A main question, though, is what is the significance of the variation?  Are you interested in variation just because they mark individual genomes within a population, or are you interested in the variation of the phenotypes of individuals?  Some genetic loci are irrelevant to phenotype and some can affect the phenotype to lesser or greater degree.  SNPs can occur anywhere so can be presumed to have a &quot;fair&quot; chance of affecting phenotype.  On the other hand SSRs can occur where only where repetitive sequences can occur (and persist where they survive selective forces). With SSRs, varying copy number in some contexts such as protein coding sequences, may have larger phenotype effects than an SNP, and thus be subject to stronger selection forces.
My view is that both SSRs and SNPs are important and it's not terribly productive to worry about general prominence or dominance of one over the other.
Reference:
(1) Guichoux, Erwan &amp; Lagache, Lelia &amp; Wagner, Stefanie &amp; Chaumeil, Philippe &amp; Léger, Patrick &amp; Lepais, Olivier &amp; Lepoittevin, Camille &amp; Malausa, Thibaut &amp; Revardel, Emmanuelle &amp; Salin, Franck &amp; Petit, Rémy. (2011). Current trends in microsatellite genotyping. Molecular ecology resources. 11. 591-611. 10.1111/j.1755-0998.2011.03014.x.