@Sanaz Janbakhsh
Assigning the Solr standalone (you can still install via Ambari Management pack) to the slaves, at least separates the Solr-Cloud Infra, from the Solr standalone.
The other consideration is what storage are you using to store the indexes on Solr standalone.
There are a number of threads where this is discussed on HCC. In summary storing the indexes on HDFS makes it easier to manage. If performance and response time it important, than you should review storing the indexes on fast disk, like SSD.