If chosing between very old model (E173) with Qualcomm chipset and a new design with Balong chipset (Huawei own brand), I would take E303 (assuming I get it for around R250). There are user reports on similiar model E303C, it gives good stable connection. Huawei says, it has Type 3i receivers, this is an advanced feature, seen in more expensive products.
Keep in mind that both devices do not support UMTS 900MHz, so if you start screaming on 8ta, you will have one more reason, as you can't use it with Cell C. There is no socket for external antenna connector.
As R400 is too high in my opinion, I would look for HSPA+ modem as a minimum, the slowest ones are sold as 14,4Mbps.