3400 ltm performance on v10.1

I'm new in F5, I've some 3400 would like to upgrade to v10 because of routing domain, ramcache and compression features. As my support vendor said it will have seious performance issue, they're not recommand v10, and suggest me directly replace all 3400 by 3600. However, I'm just have simple web (http and https) load balancing without any iRule. I also checked all 3400 only use around 10% CPU and memory. I'm not sure my Vendor recommandation is ture. Is there any prerequisite and procedure can share? Thanks!