I hear good things about Lifeline but IMO "any name brand AGM" should be pretty darn good.
I would pick the cheapest one.
When I purchased my Full River 6volt AGM's from Battery Depot I asked for a discount and they knocked off 10%. So dont be afraid to ask for a deal.... esp at the price we pay for a couple of AGM's.
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor