Sourdough starters with different smells - is this normal? I am very new to sourdough baking and gaining an interest in the subject so please forgive what may seem like newbie question.

I have two starters on the go at the moment. The first starter came as part of a "sourdough kit" which I was given as a present. It seems to be quite mature off the bat and has a somewhat 'yeasty' smell.

The second starter I got going from scratch. Just flour, water, a jam-jar and my daughters heat pad from the snake tank. (The snake died so the heat pad was going spare). I am running the heat pad at about 25 degrees celcius. Both starters are being fed daily and stored on the pad. The second starter has a more sour smell - almost stomach-acid in aroma. 

Both have similar properties - they bubble up in the same way although the second starter has patches where the bubbles are a lot smaller. The second starter started life in a small plastic cup and was transferred to a jam-jar as it grew.

So I am wondering what is 'normal'. The 'stomach-acid' smell or the 'yeasty' smell? Or is there variations on what is considered normal?

Feeding at the moment is morning and night with about 70g/70ml flour/water.
One is on the heat pad and the other is...where?  Different temps will facilitate the growth of different yeast and bacteria.  Also, your kit is likely populated with different micro flora than the starter you created.  Finally, which "smell" would you rather use to bake bread?  I would go with yeasty.  Starters get acidic fairly quickly.  This inhibits the growth of micro flora.  That is why feeding requires you to remove a significant amount before replenishing.  If you want to play, remove most of the "stomach-acid" starter, and feed the rest with flour and water (maybe remove it from the heating pad as an experiment...or try two small versions...on on and one off).  Build up again, and see if you can achieve a more pleasant aroma.