The Azhvars sing the glory of Visnu and the Nayanmars of Siva. In the Vedas all deities are hymned in the same way. The Upanishads do not speak much about deities; they are concerned with truths of the Self. Tiruvalluvar speaks about God and philosophical matters and his views are in keeping with the Vedic tradition. But the emphasis in his work is on morals and ethics. As for Tirumular, he does not deal so much with God, devotion, etc, as he does with aspects of yoga like pranayama, dhyana, dharana and samadhi. "Each great man, like each great work, speaks about a particular system, a particular path. Which of these is to be followed? " such a question arises in the minds of people. Whatever system or path you follow, follow it with faith. Do not give it up midway. In the end it will lead you to the Paramatman. In the beginning the paths may seem different but all of them take you to the same goal.
Devar kuralum Tirunanmarai mudivum
Muvar Tamizhum munimozhiyum--Kovai
Tiruvacakamum Tirumular sollum
The same idea is expressed in the "Sivamahimna-stotra". This hymn glorifying Siva is by Pushpadanta. He was a gandharva who, under a curse of Isvara, was condemned to live on earth. One stanza in his hymn says: "Trayi(the three Vedas), Sankhya(philosophical inquiry), yoga, the Pasupata system, Vaisnavism- people follow any of them according to their different dispositions. Like the rivers merging in the ocean all these paths have one meeting point, the Paramatman. "
It is this spirit of catholicism that Englishmen exclaim: "Jevhovah, Jove or Lord!". Jehovah is the Semitic God of the region of Israel, the home of the Bible. Jove is another name of Jupiter. The word "Lord" applies to the God of any faith; it is common to all religions. Realised people in the West also speak that the one Being is the same, call him by any name you like.
If the Puranas are read in an attitude of respect and humility and with the honest intention that we should benefit by reading them, there will be no cause for any confusion. We will gain the wisdom to treat them as works meant for our ultimate well-being.
For a general background, please see here