A few months back I was in the same boat. It is about $25 a hour less to rent a 172 at my local airport than the Cessna Skycatcher which is an hour away. My initinal plan was to build time with a local CFI in the 172 and transition the the Skycatcher when I was close to soloing.
I called up the preferred CFI at my local airport and was shocked with what he had to say. His response was DON'T Do it! He is a former Airforce Pilot and very well respected. His concern is the difference in flying a LSA vs. 172 or even a 152. He told me, it will cost me more money in the long run as the transition training from the 172 to the 162 would be more than a couple hours.
So, I followed his advice and I am very glad I did (he was right). I previously had 10 hours logged in a 152 and 172 (years back) and the LSA is a completely different plane to fly. In talking to my current CFI, he as many PPL who come to him to get checked out the 162 and it is a big adjustment for most of them. He swears, if you can fly the 162 well on a windy day, you can fly any 172....
I would recommend learning to fly in the airplane you are going to solo in and take the PTS in. You will want the hours in it. Something else to consider is the transition from Steam Gauges to a Glass Cockpit. That in it self took me a few flight lessons to really get comfortable with.