U-Box is U-Haul cheap and ships multiple small boxes together. 1-800-PACK-RAT gives you a single roomier steel container. Budget and box-juggling versus one durable unit is the tradeoff.
Verdict: U-Box for the lowest cross-country price if you do not mind smaller boxes and U-Haul-only pickup. 1-800-PACK-RAT for a bigger, sturdier container and steadier service.