Chip antenna PCB layouts and feedline
I think the second layout is much closer to the design guideline given by the datasheet.
Chip antennas are very sensitive for RF ground. So it is important to follow manufactures design guidelines. Also the direction of the radiation varies according to the ground clearance. The second image has a better ground plane clearance than the first. 

Please see the link below for more information.

http://info.lsr.com/LSR-Wireless-RF-Design-blog/bid/251039/Antenna-Design-Chip-Antenna-Implementation

It is important to make the length of the trace connecting from the matching circuit to the antenna as short as possible because that could add some inductance as well. Hence a shift in S11. 

If you intended to increase the length, I think it is better to calculate the transmission line width over a ground plane. 
I think it will be good to keep your PI matching pad resistors closer together as well. 

As recommended by the datasheet, antenna feed should be a 50 ohm line. You should calculate the width of the transmission line considering as a coplanar transmission line. 

Hope this information was helpful for you.