I would go with the original MP-1 Convoy. That toy just has SO much win!

+ It's big!
+ It's die-cast metal
+ Transforms from a blocky truck to a buff robot. MP10 may have a sleeker looking robot mode, but its truck mode is also too chunky at the rear.
+ Joints have freakin' hydraulic pistons!
+ Tyres have suspension
+ Ankles have suspension!
+ Shins have those vents that open up when air is pushed through them (when downward pressure is exerted on the ankle suspension)
+ Highly articulated and durable
+ Flip up communicator panels in arms
+ Chest houses Matrix chamber with internal chamber door (whereas w/ MP10 it's just part of the fender; MP-1's internals look much more like what we saw in TFTM)
+ Moving mouthplate with "grill mouth" underneath (a neat nod to G1 #76 )
+ Matrix lights up and can actually open
^all this for just 10290JPY ($113)

I really like the MP10 mould too; but IMO MP10's cab robot just isn't as jam packed full of win as MP-1, although it does come with the trailer, Roller and Spike; and $150 for the Hasbro version is just a fantastic price. So I honestly do love both MP Optimus Primes a lot, but all things considered I still regard MP-1 as the better toy.