hiarc/shredder, evaluate your elo, study

I experimented how elo is evaluated by different chess applications.

I had iPad with hiarc and samsung pad with shredder.

I put them to play against each other (I was between delivering moves).

First I tested both playing at 2500 elo- very much even match, not played to the end.

Then I did following tests:

H 1100/S 1300

H 1100/S 1400

H 1100/S 1500

H 1100/S 1600

H=hirarc was far better until Shredder was 1600, then S was clearly better.

Then I tested H 1700/S 2050.

H was little bit stronger , I stopped at the move 25.

The first tests I stopped when other side was evaluated to be about 4.0-8.0 behind.

Then I found that I was not setting any time limit to Shredder and it reacted very fast (odd?) I did a new test with 1/2 h time limit. NowS started to think.

H 1100 was still winning S 1420, after 23 moves the evaluation 27!

So, S is very friendly, evaluating you as good player about 1550 if H tells your elo is 1100. Shredder makes really bad blunders at 1500 elo level, it do not think much about below 1600 players!

True elo? If such a thing exists can be between H and S estimates.