GSM Modem Help Please!

This is the product (GSM modem) that I'm planning to buy. LINK- http://www.vegarobokit.com/index.php?route=product/product&keyword=gsm&category_id=0&product_id=482 OR http://www.vegarobokit.com/index.php?route=product/product&keyword=gsm&category_id=0&product_id=677

Which of these is better and what's the difference b/w them? Though it says a RS232 connector, it has got 5v, gnd, Rx,Tx(TTL) connectors on the pcb.So can I use it with the arduino using those TTL connectors or would I need a RS 232 ro TTL convertor Like this - http://www.ebay.in/itm/281173582097?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

PLS Also state regarding how to use it in brief if POSSIBLE.

Here's another one which seems to be a better GSM modem because it says they have got datasheets and other imp infos unlike the ones that I put in link earlier.Please also review this one!