How much data do you really need?
You said 4gb (between both lines) was working for you, so we'll assume that for comparison. This is for staying off-contract for all too, check swappa.com for phones, great site.
Cricket:
3gb (each), line 1 $45, line 2 $35 = $80 (no taxes or fees, uses AT&T, autopay option)
Verizon:
4gb (share), $70 + 2 x 30 = $130
10gb (share) $100 + 2 x 15 = $130
AT&T
4gb (share), $70 + 2 x 25 = $120
10gb - same as Verizon
30gb - $130 + 2 x 15 = $160
Sprint
4gb (share) $100 for now but will be $130 when the promo expires eoy
2 unlimited plans = $120
TMobile
2 lines, 3gb each, $100
2 lines, unlimited each, $140
Straight Talk
2 lines, unlimited (3gb 'til throttled) $90
If I only had 2 lines that didn't need a ton of data and AT&T was reliable here I'd be all over Cricket. I need Verizon coverage and have 5 lines so I am contractless and getting either 14 or 16gb (I watch and change) at $15/line + data.
A bargain isn't a bargain if you can't use your phone/data where you need to!
Of course all of the above changes when you figure in the cost of the phone or decide to subsidize and there are other carriers out there. Just tried to break it down a bit. Don't forget to calculate fees/taxes and any discounts you'd be eligible for too.
And, call Verizon about the 6gb loyalty plan, just don't jump on it unless you know it's a good deal for you. Ask them if you need a contract for that or not, I've no clue about it.