Standard they are Superb All the Rapid Range share the Same Block the only Difference with the Rapid MFR is the Reg and the Ability to just unscrew the buddy bottle without Burping
the Rapid but will only be able to use the Special 280cc MFR buddy bottle.
Mines a MK 2 Rapid in a MFR Stock with 280 standard bottle but unlike the MFR it can also use 200, 280, 400, 500, 600cc buddy bottles, So it's more versatile than a MFR.
Also all the Rapid range can inter change Cal swaps all You need is the Barrel, inner and outer probe and away you go.
Either Rapid will out shoot you and last a long