Maxxis buckshot mudder tryes??

Hi I have 2 brand new Maxxis buckshot mudders on 235 85 r16 to fit onto my 90, but need 2 more, they are quite alot to buy new, and have seen some new insa turbo dakars for £40 cheaper?? How do they compare as they look slightly different?? As long as they are the same size would it matter?? And which would you put on the front and which on the back if I did go for this set up?? Look forward to an answer?? Thanks
Oli


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I am here: http://maps.google.com/maps?ll=50.433459,-4.979948